Understanding Mono


Well-known member
Dec 28, 2015
There is a vast range of monofilament (mono) line available to anglers and there is much debate about what brand and which material is 'best'. Myths abound and anglers will often get into heated argument about the advantages of one product or material over another. Unfortunately many statements are made on these boards and elsewhere that are simply wrong or at best doubtful.

Confusion is compounded by the manufacturers and retailers themselves who give us little to no real information about their products. Adverts for mono use non-specific, subjective terms like, 'limp', 'non-stiff', 'almost invisible', 'abrasion resistant', 'supple', 'hard', 'non-reflective', 'high tenacity', 'easily knotted' and so on.

To make matters worse, the labels on the monofilament products themselves give us no information beyond diameter and breaking strength. Sometimes not even the material they're made from.

This article is an attempt to separate fact from fiction and guide anglers towards intelligent choices for leader material.

If you spot any errors or have anything you feel should be added, please reply to the thread.

What is Monofilament?
With the exception of braided leaders, our leaders are made from either nylon or fluorocarbon and both nylon and fluorocarbon leaders are monofilaments. But if someone calls their leader 'mono' they probably mean nylon. If the mono contains no information at all about the material it's made of, it will almost certainly be a nylon. An example is the very popular Maxima Ultragreen.


Basic nylons (there are several) and fluorocarbon have different properties but these days they're usually manipulated in manufacture so that one material can have some of the properties that we value in the other. All forms of monofilaments can use additives, coatings and processes to develop particular properties; stretching to reduce diameter and increase strength, coatings to increase abrasion resistance and waterproofing, dyes to change colour and resins to add hardness and increase suppleness etc.

Mono manufacture is a mass-manufacture, industrial process, much of it now done in the Far East. It's a process of melting, extruding and multiple heating and stretching. There's a video of a brand new, Chinese monofilament plant below that gives you an idea of the process.

If you want to read how it all works in massive, 500 page detail, the definitive work is here and it's a free pdf:


Fluorocarbon (Polyvinylidene fluoride, PVDF) and nylons (Polyamides) are both polymers, commonly called plastics. Polymers are long chains of repeating chemical molecules called monomers. Very roughly speaking the use of more than one type of monomer when manufacturing a particular mono creates a copolymer line. But when a mono is marketed as 'copolymer' with no other indication of its actual material it is almost certainly a nylon eg


The term copolymer doesn't really add anything useful to our knowledge of our lines - in fact we only have two types of mono; fluorocarbon and nylon.

(Fluorocarbon has its own copolymers but the manufacturers never use this term for fluorocarbon line - we don't know whether the fluorocarbon we are sold is the basic form or whether, like nylons, it also uses several copolymer forms.)

Monofilament lines can also be blends of nylons - two or more different nylons melted and mixed together. They can even be blends of nylon and fluorocarbon - as if all this wasn't complicated enough! All of this results in a lot of marketing claims that are never actually evidenced.


Fact 1. If it doesn't say fluorocarbon on the label, then it's almost certainly nylon. If it says copolymer, it's almost certainly nylon.

Because our monos can be composed of multiple combinations of monomers, plastics, coatings, plasticisers, colourings and other additives it's important to keep in mind that there are in fact only two basic kinds - nylons and fluorocarbon. The marketing guys will try to baffle us with their claims but a mono's most important attributes are determined by whether its a fluorocarbon or a nylon. All other claimed attributes are subsidiary to this.

Fluorocarbon and nylon are structurally different; both have chains made of carbon and hydrogen but nylons have oxygen and nitrogen bonds...


... while fluorocarbon has fluorine.


These structural differences create the material's properties and give the angler different opportunities in fly presentation. But it won't always be obvious what material is being sold to you and general statements about our mono are difficult to make as there is a wide range of properties for individual products. However:

The table below shows the basic attributes of the bulk materials used to make our mono. ('Bulk' here means the basic raw materials used to extrude and draw monofilament. It does not mean large spools of mono.)

Screenshot 2019-10-24 at 09.47.56.jpg

Caution Some of the attributes are changed very significantly by the extrusion and drawing process used in the manufacture of monofilament - an obvious one being breaking strength. The table is included to show the pre-production properties of the materials.

If you want more information on the chemistry of mono this is a standard work - it's a free book but you need an iBook reader and it's very technical.

Viscoelastic Properties of Polymers - PDF Free Download

Mono, Leaders and Tippets
Confusingly, these terms tend to be used interchangeably. In fact, the leader is simply the line that connects the fly-line to the hook and, with the exception of furled leaders, they are all made of monofilament.

The leader can be a length of same diameter mono or it can be tapered from a thick butt to a thin point for a more delicate turnover and presentation of the fly.

Sometimes the leader is formed of two sections the first being a thicker mono material and the second a finer one sometimes called the tippet. Both sections can be either fluorocarbon or nylon or a mixture of both.

The X System
The X system is a measure of line thickness; the larger the X the smaller the diameter. It's an old system originating in the number of times gut needed to be pulled through dies to achieve a particular thinness.

While hook eyelet diameter - which is itself determined by hook size - determines the line diameter that can be used, fish size will determine the breaking strength of line used. So a balance must be struck. As a rule of thumb, dividing hook size by 3 produces the correct tippet diameter to use. For example a size 18 hook would best suit a 6X tippet.

When a tapered leader is used, the X measurement refers to the thinnest end of the leader

The fly fishing world seems to be split on how useful the X system actually is with some people using it exclusively and others taking no notice of it at all, preferring the simplicity of measured diameter. The table below shows the relationship between the X rating and other aspects of the line.

Tippet SizeTippet DiameterPound TestFish Size
03X0.015” 0.38mm25 lb.Big Game Species
02X0.013" 0.33mm20 lb.Large Salmon
01X0.012" 0.30mm18.5 lb.Striped Bass
0X0.011" 0.28mm15.5 lb.Salmon, Steelhead
1X0.010" 0.25mm13.5 lb.Bonefish, Redfish, Permit
2X0.009" 0.23mm11.5lb.Large & Smallmouth Bass
3X0.008" 0.20mm8.5 lb.Bass & Large Trout
4X0.007" 0.18mm6 lb.Trout
5X0.006" 0.15mm4.75 lb.Trout & Panfish
6X0.005" 0.13mm3.5 lb.Trout (spooky)
7X0.004" 0.10mm2.5 lb.Trout (delicate)
8X0.003" 0.08mm1.75 lb.Trout (small flies)
The first thing to notice is that the breaking strength of the line in the table looks odd. For example, Maxima Ultragreen has a breaking strength of 6lb at a diameter of 0.22mm while the table would tell you that it 'should' be 11.5lb! This is because different brands of leader have radically different strengths and diameters. In practice, the X system is only concerned with diameter - you find the right diameter mono for the hook then check that its strength is up to the job for the fish you might catch.

Whether you find this useful is a personal choice. If you would like to see a discussion on the use of the X system, you find one in the link below. Post 37 is a thoroughgoing defence of the system.


In that thread you will also find evidence that modern mono manufactured to metric measurements don't necessarily compare very closely to the X rating that were originally calibrated in thousandths of an inch. Nor do the lines themselves always conform accurately to the diameters written on their labels. So, if accuracy is important to you, you'll need a micrometer!

Here's a video that explains the construction of tapered leaders and how to adapt the tippet. It's American so it makes a lot of use of the X system.

Breaking Strength and Diameter
For anglers, the breaking strength of mono is one of its most important attributes. Breaking strength is a function of the material and its diameter, but lines are stretched in production to change both their tensile properties (strength) and their diameter. From the materials table above and from Cap'n's below, we can say that:

Fact 2. Fluorocarbon is not necessarily stronger than nylon of the same diameter

Fact 3. Fluorocarbon is not necessarily lower diameter than nylon of the same strength

This is worth stating because it's often claimed that fluorocarbon is either stronger or thinner than nylon. This is not necessarily true. Both fluorocarbon and nylon can be strong and also thin and all variants in-between.

Cap'n Fishy's chart below shows some of the products on sale comparing diameter to breaking strength

All other things being equal, anglers would pick a line that was the thinnest they could find for the breaking strength they need. But all things are not equal.

The breaking strength printed on the spool is the amount of force needed to break an un-knotted length of the mono with a steady increase in load. In other words, it's pulled gradually until it snaps. There are no fishing circumstances where this happens: all our leaders contain knots and fish are not considerate enough to stay put, gradually increasing their pull on the line. So breaking strength information alone, while vital, does not tell the full story.

It's not intuitively obvious but the drawing process (heating, pulling and thinning) the line used in line creates a stronger line. This is because drawing aligns the molecules in the mono:


Understanding Drawn Fibers

You don't get anything for nothing though, so

Speculation: a bi-product of stretching and drawing (ie thinning), may be increasing brittleness. More on this later.

Elasticity, elongation and breakages
Monofilaments stretch. Some stretch is a good property for a fishing line because stretching absorbs the energy of sudden changes in force applied by a fighting fish. Obviously, the other components of our fishing rig do this too - fly line and fly rod - but the leader and tippet are the weakest section. We don't want so much stretch that the line is rubbery and can't set the hook or apply enough force on the fish to bring him to the net so it's a balance - a situation we'll keep confronting as other facts emerge.

Fact 4. Perhaps surprisingly, bulk fluorocarbon and nylon materials are almost equally elastic. They both stretch. This fact has been confirmed in the monofilament that we buy by Tackletour tests.

Fluorocarbon Line Tests Abrasion Tensile Knot Strength

Although you'll often hear it said that fluorocarbon is low-stretch, it's not intrinsically more low-stretch than nylon.

One of the several surprises to me in the table is that bulk fluorocarbon has a pretty good comparative impact strength (resistance to shock). This seems to fly in the face of experience.

There are many complaints on this forum and elsewhere of unexplained breakages using fluorocarbon leaders and 'back yard' tests suggest that it has much lower resistance to shock than nylon. It may be that the shock test applied to a block of bulk nylon or fluorocarbon - essentially surviving a blow from a swinging hammer - is not particularly relevant to shock testing monofilament. For that, a drop test is more appropriate and is an easy test to do for yourself. Results of one test:

"I tested 6lb (0.22mm) Maxima Ultragreen against 6.4lb (0.22mm) Greys Fluorocarbon by hanging 48” lengths of each from my garage ceiling joists and attaching a 1lb weight.

I then dropped the weight fom 47” then inch by inch until the lines broke from the dead drop.

The fluo broke at an average of 3” while the Maxima broke at 14”.

The same test with Sightfree G3 6lb, 0.18mm fluorocarbon broke at 2"

In contrast 6lb 12oz, 0.17mm Reflo Power which advertises itself as resin impregnated mono and is therefore presumably nylon broke at 9”.
(More home-based tests welcome)

There are at least two main components of what we call 'stretch' - elasticity and deformation. The total of those two is elongation. The elastic phase is when a line is stretched but will then return to its original length. When it goes beyond that point the line is permanently longer and weaker. In the stress/strain curve below Point A is the extent of the the elastic phase. (Stress is the load applied to the line and strain is how much longer the line gets as the load increases.)


Stress and strain: Mechanical properties of materials

Young's modulus is the measure of elasticity and we can see from the materials table that bulk fluorocarbon and nylon can have very similar elasticity. But fluorocarbon has very low comparative elongation. Some say that nylon undergoes stretching in its elastic phase more or less until it snaps and that fluorocarbon deforms quite early in the process of being loaded but I can find no proper evidence of this. Regardless, nylon's higher elongation should allow it to absorb energy more than fluorocarbon and may be the source of its improved resistance to shock.

Speculation: When mono is drawn, it increases in strength per diameter but decreases in elongation so thin line (in relation to its strength) will probably have lower shock strength than a thicker line because it will have been stretched more. This brittleness may be exacerbated in fluorocarbon because of its inherently low elongation.

More information required Mono is a thermoplastic. Thermoplastics exhibit a behaviour called viscoelasticity, that is they behave like both solids and liquids under stress. Nylon polymers may exhibit greater viscous behavior than fluorocarbon. The viscous behavior kicks in at high deformation rates, and helps to partially support the tensile stress in the filament making it less likely to fail.

One piece of possible evidence for this effect is that when load is removed from a viscoelastic material it dissipates heat. Cap'n has photographed the ends of failed lines that have broken under extreme load. They show a 'pin head' effect that looks very similar to what happens to mono when you put a flame near to it. Is a release of energy at the break causing this effect?

So this may be why we hear complaints of fluorocarbon's breakages in circumstances of sudden shock - catching two fish simultaneously, violent dashes for freedom at short range where there is less elasticity in the whole system of rod, line and leader, excessively hard strikes, 'cracked off' flies and so on.

The perception that fluorocarbon is susceptible to shock breaks may be also heightened by anglers using line that is simply too weak for the job, based on mistaken ideas of the material's properties. Fishing with very low diameter fluorocarbon - and to a lessor extent, nylon - risks break-offs, so should be reserved for situations where it is absolutely necessary.

All that being said, and whichever type of mono you are using, it seems that there are good reasons to change your leader after it has come under very high stress or has been abraded.

But there is even more to line strength than this.

Water absorption
Fact 5.
Fluorocarbon is waterproof. Nylon is not, it absorbs water from both the air and the water.

As nylon absorbs water it becomes more supple but it also becomes weaker. Most reports say about 10% weaker.

Suppleness is sometimes wanted and sometimes not. In some circumstances it may improve presentation by allowing more freedom of movement to the fly in the water. But the stiffer the line, the less chance there is for tangles and the better the turnover of the leader.

So there's yet another trade-off to be made.

Knots probably deserve a post all to themselves, it's yet another topic that gets people hot and bothered and where many opinions abound. As fluorocarbon and and nylon have differing knot strengths it's briefly included here.

We have to put knots in our leaders; a minimum of two - to attach the fly and to connect to the fly line - and often several more for droppers and tapers.

Fact 6. All knots weaken all types of line. Worth reading that again. All knots weaken all types of line.

So when you're fishing with 6lb line, you're not actually using 6lb line.

For example, when Seaguar Grand Max Fluorocarbon line was tested it averaged a breaking strength of 9.98lb without a (Uni) knot and only 5.99lb with a knot. There are more tested here:


In that paper you'll also find a maddening difficulty when comparing breaking strength of mono. The mono almost always has an actual breaking strength different to that advertised on the label, sometimes more, sometimes less - 15lb mono varied by brand from a measured 19.48lb (Seguar) to 12.26lb (Cabelas Premier). So you'll find some lines with a quoted knot strength of 120% which rather removes the purpose of showing how much a knot reduces the strength of a line.

Fact 6a. Some knots are better than others.

Testing shows that the worst kind of knot to have in your leader is the simple overhand knot, luckily this is not a knot we would ever use, but sadly it is the knot we get when our casting goes a bit wrong - the so called wind knot. If you get one, either undo it or change the leader.

Fact 6b. Nylon has higher knot strength than fluorocarbon. Yellowstone found that all mono is reduced in strength by 20-30% on average but in some fluorocarbon lines knots reduced breaking strength by 50%.

Speculation: nylon is relatively supple - especially when wet - which may lower bending forces which in turn puts less strain on the knot. Could nylon's improved knot strength offset nylon¡s loss of strength when wet? Possibly.

So which knot is best?

It may seem like a bit of a cop-out but probably with the exception of the overhand knot, the best one to use is one that you are very familiar with. One that you can tie automatically, almost without thought. One that you know just by the look and feel of it when tied that it¡s right. BUT

Tip When you've made the knot test it! If it's a hook to mono knot, put the hook in the finger hole of your forceps or the hole in a zipper tag and pull on the line like crazy. You'll be surprised how many of your knots slip. (You can tell when a knot has slipped rather than broken because it leaves a tiny curly piece of nylon - a 'pig tail' - at the end of the mono where the stress has deformed it.)

If you're new to fishing there is one very good knot that you can use for almost all purposes - reel to fly line, fly line to mono, mono to mono, mono to dropper, mono to hook. The Uni knot

Otherwise knot choice tends to be personal preference. From experience, many UK fly anglers use a tucked half blood knot (aka the improved clinch knot) to tie mono to hook and a three turn water knot (called in the Yellowstone data below a double surgeon's knot) to join mono to mono. Though, of course, many use other knots - just pick a good one and stick to it.

Yellowstone Anglers did an extensive series of tests on knots



A good resource for knot info:

Fact 7.
Despite advertising claims and although fluorocarbon and nylon have different refractive indices, neither is invisible in water.

This 'invisible' property of fluorocarbon was highly hyped by manufacturers in the early days of its introduction and it still exists in their adverts, though now usually moderated to 'almost' invisible. To counter this, some nylons added colourants to make similar claims: Maxima Ultragreen again:

Virtually invisible to fish as light rays are absorbed rather than reflected

Fluorocarbon may be a little less visible - because its refractive index of 1.42 is closer to water's value of 1.3 than nylon's of 1.53 but observations in real fishing circumstances are that both are visible and fluorocarbon can have 'flash' in sunny conditions - a point alluded to in Maxima's claim above. Cap'n's video clearly shows this effect:

There's a lot of problems with the refractive index claim itself:

The first is how do we know what the refractive index of the material we are using is? It's not on the label. Unless it says 'fluorocarbon' on the label we have no idea what the mono material is. Nylon isn't a single compound, it could be many different copolymer combinations and have all sorts of additives and colourants. Even fluorocarbon has it's copolymers - we have no idea what the refractive index of the stuff we use is.

Second, what water? Distilled at standard temperature and pressure as the standard. Or the stuff we actually fish in, peat stained, full of micro-debris, cowpoo and algae?

Third, what light conditions? Refractive index varies by wave length. What is the wave length of light 6 feet down in a spate water?

Personally, I think you can ignore all claims about visibility of different materials but I would not fish a clear line like fluorocarbon (or a clear nylon) in bright conditions because of the perceived flash.

There are occasional days when two anglers in the same boat differing in tackle and technique only by the use of nylon or fluorocarbon catch differing numbers of fish. When the low-catch angler switches to the other's mono, he starts to catch too. The difference appears to be due to differing visibility (although different sink rates may also be a factor - see below). Unfortunately, which mono to choose in which conditions can only be determined by trial and error, but it would seem reasonable to suppose that because of fluorocarbon's observed flash it would be not the first choice in bright conditions.

Floating and Sinking - surface tension
When lengths of fluorocarbon or nylon are dropped onto calm water straight from the spool they will both float.

Fact 8. Although fluorocarbon and nylon are both denser than water and will both sink (at different rates), neither can routinely break through the surface tension of the water unaided, particularly at fine diameters in a still-water flat calm.

Line 'degreasers'* help sink both types of mono by lowering the surface tension around the line. It's the detergent in them that does this but unfortunately it is water soluble so you need to repeat the application every few casts. This is a great demonstration of detergent and surface tension.

A floating leader bends the surface tension of the water making it more visible to the fish so it's good practice to sink the leader using a sinkant when using a dry fly.

Cap'n Fishy's photos taken from underneath the fly demonstrate this

Leader floating

Leader sinking

And another

*Recipe for home made line degreaser
1. Fullers earth (eBay) or use ground up cat litter (unused!)
2. Washing up detergent (unsented if possible)
3. Glycerine (chemist or eBay)
Mix roughly equal amounts of glycerine and detergent into a a handful of fullers earth until it's a stiff paste. Stick it into a container of your choice - old fashioned film cases were popular, I use a small vaseline lip gloss tin.)

Once through the surface tension ...

Fact 9 Fluorocarbon sinks faster than nylon.

To make your leader sink while dry fly fishing in calm conditions you need to regularly treat it with a sinkant that contains a detergent (which locally reduces the surface tension of the water).

There are observations that once nylon has been used for an hour or so its ability to break the surface film unaided is increased.

Speculation: it's not clear why this observed phenomenon occurs. Even if soaked in water for 24 hours nylon does not sink straight off the spool. Some combination of water absorption and repeated line treatment may be responsible.

Another observation is that thin diameter fluorocarbon is harder to sink in a flat calm than nylon.

Floating and Sinking - sink rates
Fact 9.
Once through the surface film fluorocarbon sinks faster than nylon. This is because fluorocarbon is denser than nylon and sinks roughly 3 times faster.

When the sink rates of Airflo G3, 0.23mm fluorocarbon and Maxima, 0.23mm nylon were tested, the fluorocarbon sank at 2.4” per second while the nylon sank at 0.8” per second.

There are some uses for this differential sink rate:

- when slowly swinging flies around in a breeze and trying to get a little deeper (where a weighted fly would drop too quickly and/or change the presentation of the fly) fluorocarbon can help.

- when dry fly fishing with small flies left static for a while, it is often better to use nylon than fluorocarbon as, when the leader does sink, nylon sinks slower and will be slower to drag the fly under.

- when river fishing with nymphs in shallow water the use of nylon rather than fluorocarbon prevents the fly being taken down too quickly and snagging.

- conversely when nymphing for grayling the use of fluorocarbon may get the fly down to the fish quicker.

- when using fluorocarbon with a dry fly it may be pulled under water when lifting off to recast - the sunken leader can also pull the fly down requiring the angler to constantly dry his fly. I can also produce a 'splashy' lift-off.

- when anglers want their flies to float for a while then sink they often use fluorocarbon rather than nylon.

There will be more, but the main points to consider are where the fish are and how the choice of material will affect the presentation of the fly to them.

Fluorocarbon is more sensitive than Nylon

Sensitivity is said to be important in feeling takes. Fluorocarbon is significantly denser than nylon giving a claim that it is more sensitive. This is said to improve the contact between the fish and the angler allowing him feel the fish and to set the hook more effectively at the take.

How important the difference between the two monos is in a real fly fishing environment where only a short length of leader (typically 9-12 feet) is used and where the fly line and flexibility of the rod itself has considerable impact is untested. In contrast, in some sea fishing situations where a hundred meters or more of line can be in use a considerable effect may be felt and maybe the more reasonable claim - and also its origin.

Fluorocarbon has greater abrasion resistance than nylon.

Fact 10. Nylon in its raw, bulk material form is harder, ie more scratch resistant, than fluorocarbon

Another surprising finding. Abrasion resistance could be important if fishing in circumstances where a large fish could pull the line against rough obstacles such as coral in salt fly fishing or rock in rivers when fishing for salmon or large sea trout. In most fly-fishing situations for trout this will be unimportant.

There are mixed results when empirically testing abrasion claims; TackleTour found an average of 30% improvement in abrasion resistance of fluorocarbon, compared to a Trilene XL nylon when it was dry and 50% when wet. However, Salt Strong found the opposite result - fluorocarbon was significantly less abrasion-resistant than ordinary nylon. And Yellowstone Angler's couldn't find any difference at all!

It may be that this property is brand dependant and individual testing is necessary. Or perhaps different testing methods give differing results. Until there are consistent results from empirical tests, advertising claims of superior abrasion resistance need to be met with some skepticism.

Environment and Degradation
Fact 11.
The UV in daylight degrades nylon. Fluorocarbon is not degraded.

Keep your nylon in the dark.

Don't throw either mono away on the bankside but especially fluorocarbon as it will stay in the environment forever.

Fact 12.
Fluorocarbon is more expensive than nylon; sometimes considerably so.

A brief look in a fly fishing catalogue will demonstrate that the price difference between leader material of the same brand can vary from a few pence (Climax; 49p) to several pounds (Hardy; £11, Rio £7) and often by a factor of x2 difference or more.

This is partly because fluorocarbon bulk material and extrusion processing is more expensive than for nylon but more probably simply because the manufacturers have found that it can command a market premium.

Of course carrying two sets of mono rather than one doubles mono cost generally which may be a consideration for some. But on balance, because we use so little mono the extra cost is low and the benefit of having both tools available to us offsets any additional cost for most of us.

I've resisted making recommendations for mono as it will create a lot of trouble - everyone has their favourite, but there will be people who read this thread that only want to know what to buy. So here goes.

Nylon Probably the commonest and most recommended brand of nylon by people here is Maxima Ultragreen. It's low cost, reliable and has been around forever.

Also if you're looking for the bog standard, all-things-to-all-men, everyday, use-nothing-else mono for fly fishing for both trout and salmon this seems to be The One.

Drennan Subsurface is a very similar and also much loved product.

For dry-fly, flat calm work, where the fish may be leader-shy and low-diameter nylons may work best, people seem to use either Reflo Power or Stroft GTM.

Fluorocarbon Fulling Mill and Berkley Trilene seems to be a good, low cost, standard Fluorocarbons with Airflo Sightfree G3 being the low diameter preference. Seaguar, while expensive, seems to be the choice of salmon anglers.

Bulk Buying
Our mono is manufactured by the kilometre and sold to the brands by the kilogram for embarrassingly little. Cost-conscious anglers can offset the brand inflation effect by buying bulk from Alibaba. A kilo of bog standard nylon PA6 can be had there for $3 and would last this forum of anglers a lifetime! But buyer beware, until you use it, there's no telling how good it is.

Perhaps a more sensible approach is to buy larger quantities of well known and tried and tested brands - 100m or 200m spools of Maxima, 300m spools of D.A.M Tectan for nylon; 200m of Airflo G3 or 250yds of Seaguar Red Label for fluorocarbon.

Here's Cap'n's chart on the cost of mono organised cheapest first.


Both nylon and fluorocarbon mono leader materials differ in their properties and therefore differ in the uses anglers can put them to.

However, manufacturers give us little to no real information about their products and there are no robust, independent scientific studies comparing brands that would help us. As a result anglers need to test lines to find the versions they prefer by experiment or recommendation matching them to the forms of fishing they are doing.

Given the wide variety of circumstances a fly-fisher can find himself in it's impossible to be prescriptive in leader material choice, hopefully though a fuller understanding of the material's properties allow a considered decision to be made when on the water.

Overall we can say that so long as we understand what we're doing, either material could be used as a general purpose mono - there are anglers that only use nylon and anglers that only use fluorocarbon and both materials will catch fish. After all, as one member here said 'it's just tippet'. But given the above, it seems clear that intelligent choices based on the individual properties of both materials and fishing circumstances are likely to both catch more fish and to lose less due to breakages.



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Well-known member
May 17, 2006
Central Scotland
I'm not sure I understand this
''(When Seaguar Grand Max Fluorocarbon line was tested with and without knots it averaged a breaking strength of 9.98 pounds with a knot and 3.99 pounds less without it. )''



Well-known member
Dec 28, 2015
I'm not sure I understand this
''(When Seaguar Grand Max Fluorocarbon line was tested with and without knots it averaged a breaking strength of 9.98 pounds with a knot and 3.99 pounds less without it. )''

It's ugly phasing, I'll change it.

Tested breaking strain without the knot was 9.98lbs and with the knot it was 5.99lbs. They used a Uni knot.

I think most tests use a single overhand knot - equivalent to a wind knot.


Well-known member
Nov 14, 2008
West Riding of Yorkshire
I've just been for some leader line while its on offer, specimen camo fast sinking for subsurface fishing and HD floater high buoyancy for anything on the top.
Also worth noting that pre-stretched nylon isn't as good for knot strength (especially to the hook) as the standard, however theres a lot of different formulae so its dependent on what you use.

Rio do some interesting test on line and knots


Well-known member
Dec 31, 2017
I had my first ever problem with Maxima Ultragreen this season.

One of their pointless rubber bands must have escaped and got sucked onto my electric bilge pump and wound tightly round the impeller shaft inside the sealed unit. A write off.

Apart from that. Perfect. :thumbs:


Well-known member
Sep 28, 2017
Where I want to be
Fact 9 fluo sinks faster than nylon.

This is because fluo is denser than nylon. But this effect is not large; both will sink relatively slowly - weighted flies will sink far faster. Even so, some anglers find a use for this relative difference when slowly swinging flies around in a breeze - particularly buzzers.

Even wet fly fishers in a fast drifting boat can see the difference in the depth achieved with fluoro over nylon. The effect is larger than you suggest, a foot difference in the depth over the cast is possible. This might not seem like much but it can make all the difference to catches.
I might have mentioned in the past that I never use fluoro but I have seen the difference in sink rates first hand hundreds of times, to say the effect is not large seems a stretch to me.

I would also question the value of the raw figures for the materials you quote in the table. I'm sure they are correct but they do not say what state the materials were in when tested. I suspect none of them were tested in the form of manufactured fishing line. A 1 inch nylon bar if a very different animal to a 0.010" nylon line - them mollycule thingies may well be arranged very differently.



Well-known member
Dec 21, 2014
Well, fact 1 is wrong, flouro has an r in it indicative of containing flourine, and native is nonsensical- bulk would be more apt. Interesting start though.


Well-known member
Dec 21, 2014
A 1 inch nylon bar if a very different animal to a 0.010" nylon line - them mollycule thingies may well be arranged very differently.


Exactly. Bulk properties aren't indicative of highly processed and refined structures. Folding a lump of iron 500 times to make a samurai sword etc.


Well-known member
Dec 28, 2015
Well, fact 1 is wrong, flouro has an r in it indicative of containing flourine

I opted for fluo because no angler ever says fluoro and if I'm going to abbreviate it may as well be as short as still makes sense. The 'r' has no added value - fluorine's chemical symbol is simply 'F'.

and native is nonsensical- bulk would be more apt.

Maybe, I chose native as I suspect that more non-chemical engineers would know what I meant...

Interesting start though.

Lots to bottom out yet but I'm not sure where it can come from.


Well-known member
Dec 21, 2014
I opted for fluo because no angler ever says fluoro...
I say fluoro all the time. Think most lads i fish and banter with do too. Wouldn't know how to pronounce fluo. Is it like welease wodewick?


Well-known member
Dec 28, 2015
Even wet fly fishers in a fast drifting boat can see the difference in the depth achieved with fluoro over nylon. The effect is larger than you suggest, a foot difference in the depth over the cast is possible. This might not seem like much but it can make all the difference to catches.

I'll try to find some proper sink rates.

I would also question the value of the raw figures for the materials you quote in the table. I'm sure they are correct but they do not say what state the materials were in when tested. I suspect none of them were tested in the form of manufactured fishing line. A 1 inch nylon bar if a very different animal to a 0.010" nylon line - them mollycule thingies may well be arranged very differently.

I agree. I tried hard to find equivalent data for mono but the data sheets I found had practically nothing. It may be out there, in which case I'd love to see it.

Even so, some of those values are core to the material - absorption, density, refractive index. Others are more likely to change in manufacture - elasticity, tensile strength.


Well-known member
Feb 27, 2009
West Lothian Scotland
I'll try to find some proper sink rates.

I agree. I tried hard to find equivalent data for mono but the data sheets I found had practically nothing. It may be out there, in which case I'd love to see it.

Even so, some of those values are core to the material - absorption, density, refractive index. Others are more likely to change in manufacture - elasticity, tensile strength.

I've got the testing stuff sitting from the last time I compared nylon and flouro, I'll film it tomorrow and post the results for all to see.
My memory is a bit dodgy but I think flouro was going on 7 seconds for 8" and nylon was 19 seconds for the same 8 inches.


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