As a kid, the first thing I remember about fishing line is the number with an “lb” and “test”.  Since I was in America, this of course referred to tensile or breaking strength of this particular fishing line.  Back then, our choice for fishing line was more or less monofilament.  As a kid, I was focused on two things: 1) the pound test of the line and 2) the brand for which I had seen more commercials during a show of In-Fisherman.  Once I started fly fishing, I had to learn the “X” system, since the people I learned from didn’t really say “use four or six pound”.  They spoke in terms of 5x, 6x, 3x etc.  Eventually, I became familiar with the pound test associated with the “X” system, and pound test has become more and more popular as a reference point.  However, over 20 years of fly fishing later, I’ve come to understand the use of pound test (breaking strength) as a simplistic and often misleading criterion for choosing my fly fishing leader and tippet.

The reason for this statement is that the pound test of a line has been a misleading shorthand for a specific type of line, and thus has taken away from other aspects of lines, as long as I can remember.  This encourages folks to buy a fly fishing leader or tippet according to simply the “X” value or the pound test.  The fact of the matter is that there are well over a dozen factors to consider when buying a line.  These factors are taken into consideration naturally after one changes his/her mindset on buying a fly fishing leader or tippet.  The reason for choosing a leader or tippet material can be divided into two main parts: “the grab” (presenting the fly and fooling the fish into striking) and “the nab” (brining the fish to hand after it strikes the fly).  The following will layout the factors involved in selecting leaders and tippets with these two factors in mind.  Part 1 covers “the grab”.


The first consideration when trying to catch a fish is actually fooling or triggering the fish to “grab” the fly.  Pound test makes absolutely zero difference on this stage of the game.  That’s right, the point at which your line will break plays zero role in getting a fish to take your fly.  This is a critical step in choosing leaders and tippets: you must separate out the elements of these lines.  There are 5 major factors that should be considered when choosing a fly fishing leader or tippet for presentation: suppleness/stiffness, diameter, sink rate, color, and visibility.  Two stages of the presentation play with these factors: 1) presenting the fly with the cast and 2) presenting the fly in or on the water.


Two of the factors (suppleness/stiffness and diameter) affect the presentation through your casting.  First, the diameter is hugely important.  Diameter has been so important for fly fishing historically that the use of the “X” system has been the symbol used to buy tippet and designated the final tippet size on tapered leaders for hundreds of years.  Fly fishing tippet was made from a translucent membrane within the gut of the silkworm, which is about 12-18 inches long and is still sold today.  The diameter of this membrane was measured in inches in England after the worm’s importation into England from China.  Thus was born the “rule of 11” which means that the tippet size “X” value (3x, 5x etc.) plus the diameter (in thousands of an inch) must equal 11.  In this way, you can determine what the diameter is by subtracting the X-factor from 11.  Example: 2x tippet has a diameter of .009 or 11-2 = 9 (.009).  This holds true up to 0x.

8x003 (.076 mm)1.5lb (0.7 kg)
7x.004 (.102 mm)2 lb (0.9 kg)
6x.005 (.127 mm)3 lb (1.4 kg)
5x.006 (.152 mm) 4 lb (1.8 kg)
4x.007 (.178 mm)6 lb (2.7 kg)
3x.008 (.203 mm)8 lb (3.6 kg)
2x.009 (.229 mm)10 lb (4.5 kg)
1x.010 (.254 mm)12 lb (5.4 kg)
0x0x .011 (.279 mm)14 lb (6.4 kg)

Why is diameter so important? Because the diameter of your line determines the power.  The diameter of your tapered leader and/or your final tippet size determine energy dissipation.  Practically speaking, the larger the diameter, the more power you will have when casting.  The power in your fly casting is lost when small diameters are attached to the fly line, and a larger diameter will also have more weight and thus inertia once it gets moving.  The length of your fly fishing leader affects power as well, but this factor is tied up (no pun intended) with leader formulas, which are another article/book? entirely.  Even energy transfer happens through consistently similar diameters within the tapered leader.  All things being equal, 5 feet of .009 tippet will be infinitely more powerful than 5 feet of .004 diameter tippet.  One is better for casting streamers on trout lakes, and the other is better for tiny flies on spring creeks.  You can use 1,000 lb. test to try and get more power in your cast, but if your 20 lb. test has a larger diameter (all other factors being equal) it will still cast further with the same amount of effort.  Once again, weight will affect the inertia of the whole rig but is usually difficult to calculate unless you are using wire or something like that.  For this reason, diameter serves as a more consistent element when choosing your fishing line particularly with the same material.

Fly fishing leader suppleness.The other factor to affect casting is the suppleness/stiffness of your mono, fluoro, or braid.  A simple rule is all other factors being equal, the stiffer the line, the easier it will shoot and turn over a fly unless cold temperatures are so bad that your line will not straighten out.  Think about a limp spaghetti noodle vs. a piece of monofilament of the same thickness and length.  If you tie a nymph on the noodle and let it go, nothing will happen (hopefully no one actually attempts this).  However, the stiff piece of mono will use its potential energy and spring forward.  Incidentally, fly line cores reflect this phenomenon, so that fly lines with stiff mono cores shoot much better than lines with limp cores (heat or cold affects this effectives).  There are some things to keep in mind though.  How hard do you want the line to hit the water?  How big is your fly?  A supple line is usually more desirable for those softer presentations with longer leaders and small flies.    A final word about leaders and tippets is that very stiff lines have sometimes impeded really tight loop formation while casting, so if you want ultra-tight loops, choose a line that isn’t as stiff as a board.  So, when choosing a fly fishing leader and tippet for casting purposes, consider diameter and stiffness above all else, which are really two peas of the same pod.


If you can’t get the fly to the fish, then everything else is meaningless.  Once the fly is on the water, none of the qualities of the line that aided you with casting will necessarily help you fool the fish.  In reality, you choose a line that gives you the best of both worlds.  However, now you’ve entered the fish’s world where our fly should be most of the time anyway since, as Gary Borger puts it, “we’re not fishing for owls.”  All of the factors important for presentation, suppleness/stiffness, diameter, sink rate, color, and visibility play a role in coaxing fish to take the fake with varying degrees of importance.  A short video helps in demonstrating this below.  See the article video on mono vs fluoro with underwater footage.

Fly fishing leader color.Let’s start with color.  There are mainly two reasons for choosing different colors of line: 1) because it blends in better with the fish’s environment, 2) so that you can see the line better.  Why would you want to see your fly fishing leader or tippet?  The only reason is to detect a strike, whether that means seeing the line jump/move or tracking your fly by watching the tippet/leader.  Professional bass anglers will use brightly colored lines for this reason in certain instances.  This becomes very important for finesse fly fishing for bass (largemouth and smallmouth) as well, although I myself have never gone to the extremes of using bright yellow tippet.  I do use very small indicators, however, which is more or less a way of compensating for my clear line, and other nymph fisherman, such as George Daniel, use different colored lines in their fly fishing leader construction.  The first reason, i.e., blending in with the fish’s environment, probably seems more obvious to most anglers.  In this case, the idea goes that you will catch more fish if your line is more inconspicuous, and thus, you should try to match your line to the conditions.  Pretty obvious here.  However, it is still up for debate on how much line color affects a fish’s likelihood of eating your fly.

Fly fishing leader visibility.Number two, and related to being inconspicuous, is line visibility.  This factor to me is one of the most exploited (by line manufacturers/marketers) and misunderstood of all the factors.  It is so easy to take one aspect of line choice and make it a panacea for our fishing woes or reason for our fishing success.  There may indeed be some merit in having a line that gets close to water in its light-refraction index, since glare can both attract and scare fish, but think about line invisibility for a second.  The idea of “invisibility” assumes that 1) a fish can’t see your line and 2) that if the fish sees the line, it will have negative associations and not take the fly.  What about that gigantic hook sticking out of the butt of the fly, lure, or live bait?  Even on our smallest imitations, midge pupae, we still have a hook point sticking out that is nearly 50% as long as the actually tied portion.  In order to get even more hook-ups we must now have invisible hooks, right?  I’ve never understood “the invisibility of line” concept.  I do, however, believe that a certain level of inconspicuousness must be achieved in certain clear water situations to improve opportunities just a bit.  That does not mean making the line invisible, i.e., making a fish physically unable to see the line.  There have been zero studies to my knowledge that have proven fish can’t see any line at all in the water.  I will admit that there are some qualities of fluorocarbon that allow it to be less obtrusive but would never claim any line is “invisible to fish”.  Line colors and visibility as a deterrent need much more research.  The few that have been performed have revealed that bass can see monofilament that is very small in diameter, around .006, and that they can distinguish between colors quite easily.  Bass can also negotiate their environment and catch prey effectively without their eyes.  A summary of these studies can be found in O.D. Colin J. Kageyama’s book (159-160).  I tend to agree with Dr. Kageyama’s opinion about anglers’ going to a smaller diameter to fool fish.  He states, “It is likely that success is more related to reduced line drag, resulting in greater lure action, sensitivity, and control [not invisibility].”

Given the doubt on how effective less visible line really is, we need to think about “invisibility” in a different way.  Something becomes invisible for all intents and purposes when focus is placed on something else to such a degree that we see only that object.  Focus is the key to coaxing a fish into striking, that is, making the fish focus on our fly through triggers.  The general phenomenon is called “inattentional blindness” or “perceptual blindness” (often linked to “change blindness”) and this is just one way in which things become “invisible” within plain sight.  In order to focus, e.g., catch a fleeing fish, suck in one of millions of spent tricos, or tip down to engulf a crayfish, a fish must block out other things.  If you are unconvinced, then see examples here and here.  Read more about it here, or get an entire book on it here.

I have seen countless examples of this phenomenon while fishing.  Most recently, I was fishing in a shallow bay for northern pike.  The bay was filled with northerns that would spook quite easily when they saw us coming—it was difficult to see the fish because of the huge amount of weeds in the bay.  However, there were many instances in which we could see a fish, cast a fly to the fish, and then coax the fish into taking the fly even within 5 to 10 from the boat.  Once they had the fly in their face, they focused so heavily on the movement and enticement of the fly that it was all that mattered.  The large boat, the thick bite tippet, the color of the fly line all became less important if not “invisible” to the fish that was watching every move of the fly in most cases just sitting and undulating in the foot-and-a-half deep water.  Had I jumped into the water, the stimulus would have been sufficient enough to bring the fish back into a fleeing mode.

We must account for the millions of fish (including thousands of world records) caught on plainly visible line.  We must conclude that fish eat our fly all the time when the fly fishing leader or tippet is physically visible.  Therefore, it is something else that causes a fish to take our fly, not the relative invisibility of our line.  Because the fish must focus on the fly, it is the way your fly moves or floats that is the most critical component to our leader or tippet, not its invisibleness.  In other words, should we use forty pound test fluorocarbon and its gigantic diameter with a size 22 midge pupae, even though it is “invisible” to the fish?  How your fly moves trumps “invisibility” every time, and other attributes of your line affect this aspect and are thus more important than “invisibility”.  Incidentally, this is why a loop knot to the fly is critical in most cases.  This topic needs much more research, particularly with inattentional blindness with respect to animals (not humans).  As far as food for thought, think about the intelligent greyhound that chases the “little rabbit” around the racetrack or the cat that finds a moving piece of string irresistible.

Stiffness/suppleness and diameter often do not receive enough emphasis.  This is where the balancing act takes place, since these two factors are the most important for casting.  A supple tippet or leader is almost always better than a stiff one, and the smaller the diameter, the more flexible and supple a line can be.  Supple, small diameter lines allow a dry fly to remain drag-free on the surface and less susceptible to microcurrents.  Nymphs move freely and naturally within stillwater environments and the currents of rivers.  Streamer patterns achieve their best movement as well, able to dart back and forth or side to side with greater ease.  This is only as far as coaxing the fish to “grab” the fly goes.  So, with all things being equal, I want the most supple and smallest diameter tippet and leader I can get for presentation purposes with as much action as possible, but a balance must be met for optimal casting and in-water presentation.  If you want more of a gliding movement out of your flies, then a stiffer high diameter line will impede the movement of your fly.  Also, a quick rule of thumb that has been used for years is to divided your fly by three and round up (with a 2 remainder) to determine the X value.  Size 14 fly : 14/3 = 4 remainder 2, which is 5x.  This is, however, just a quick and easy, but also imperfect, method.

Diameter goes hand in hand with the final factor, sink rate.  Essentially the smaller the diameter, the faster a line will sink by virtue of less water resistance.  However, breaking through the surface film can be difficult with micro diameter lines without weight.  Keep this in mind when you want flies to sink fast and easily or when you want flies to hover in the mid-depths, resist sinking, or float.  Situations such as these are when you are casting over vegetation, when you want your fly to hover in between strips, or you are fishing a popper etc.  You must be aware of this when choosing tippet or designing a fly fishing leader, since you may have a leader that sinks weirdly if you have all sorts of different diameters and sink rates involved.  Your knot will also affect how fast your fly sinks, and a loop know will allow your fly to have more action and sink faster.  You need to put these all together depending on what you want your fly to do.

Your presentation drives your fly fishing leader and tippet selection.  You need to think about the casting demands of your fishing environment and then envision exactly what you want your fly to do once it hits the water.  After this, you just need to find the tippet and leader that do all of this best.  At this point you haven’t thought about pound test (breaking point) because you haven’t even set the hook yet.  Neglect the “grab” and the “nab” never happens.  We cover this in the next article fly fishing tippet and leaders and setting the hook.

Share This



You have Successfully Subscribed!