Published Nov 24. 2002 - 16 years ago
Updated or edited Jul 14. 2018

Fly line anatomy

My fly line doesn't understand me! And I don't understand it... This article tries to explain tapers, densities, coatings, memory and all the terms used for these expensive pieces of string.


The number of actual manufacturers of fly lines in the world is small. The rest get their lines produced by the few. We have tried to isolate those that develop fly lines under their own brand, but some of these are most likely produced by the same small range of select manufacturers.

Lee Wulff
Michael Evans

I will start by setting some terms straight. The following discussion will refer to the different parts of the fly line by these names, and the different parts can be seen on the drawing below.

Fly lines come in two basic shapes:
DT or Double Taper, which is a symmetrically built line, usually equally thick over all its length and with a identical taper in each end
WF or Weight Forward, which has a thick part and a thin part and different back and front ends.

I will illustrate the terms with a simple WF line.

Anatomy of a simple WF line
Fly line terms

Line tip: the front part of the line, equally thin over its length, where the leaders is attached
Front taper: the transition between the tip and the belly
Belly: the thick part of the line
Rear taper: the transition between the belly and the running line
Running line: the long, thin part of the line, which connects to the backing at the reel end
Head: the tapers and the belly as one part

A typical WF line has a short tip of a few inches or maybe a foot (10-30 centimeters), long tapers, maybe 3-6 feet (1-2 meters) and the head is mostly around 30 feet or 10 meters. The rest of the line up to about 90 to 100 feet or about 30 meters consists of the thin running line, which is equally thick (or thin) all the way. A DT line has no running line, but is one long belly with an identical taper and tip in each end.

Complex tapers

In spite of the fact that a fly line only consists of fairly few parts, they are surprisingly complex and especially shaping of the taper is a science in itself. There is a wealth of different designs and each manufacturer has their own ideas and designs.
The selection of materials is highly determining for the many characteristics of the line, and is usually a well guarded secret.
The production methods also vary and where some producers make lines by coating a core with different amounts of material, others extrude their lines from thicker pieces of material.

Let's look at the tapers first. As already mentioned, these vary, but there are some common types. The effect of the different tapers is often discussed - even by experts - but it all sums up somewhat as follows:

Double Taper
Double Taper: a straight line with a tip in both ends is a typical presentation line, which is well suited for fine arcs and delicate casts. The line excels in line control, like when doing roll casts, mending etc. The DT line is used for dry fly fishing, but is not uncommon on two hand salmon rods used for casting types such as spey casts.

Weight Forward
Weight Forward: an ordinary line with a belly is the universal line that combines longer casts with an acceptable presentation. The casting weight is gathered in the front end of the line, which pulls the thinner and considerably lighter running line, yielding longer casts over delicacy.

Casting Taper
Casting tapers: a weight forward taper specifically designed for longer casts. The rear taper is longer than on a basic WF line thus concentrating the weight even closer to the tip. Casting length is increased, again sacrificing a little delicacy. These lines are sometimes referred to as Distance Tapers (Scientific Anglers) or QuickShooter tapers (Rio).

Wind Taper
Wind tapers: has been tapered to be suitable for casting under windy conditions with a short belly and a very long rear taper, producing a hammer like weight distribution, appropriate for fighting a wind. Product names include Wind Taper, Salt Water Taper, WF Performance (Guideline) and others. Rio's wind taper is called Delta Taper, referring to a triangle, but reversed in comparison to the later mentioned triangle taper.

Compound Taper
Compound tapers: refers to tapers built from more than one transition. Compound tapers have three or more lengths of equally thick line parted by each their taper. The most common compound tapers are different variations of the wind taper having two or more rear tapers.

Triangle Taper
Triangle tapers: in this case the front taper is long and will produce a very smooth transfer of power through the line to the leader. This generates an extra delicate presentation. Some very long triangle tapers are utilized for two hand rods and underhand and spey casts.
Most known is the brand Lee Wulff's Triangle Taper, but others have names such as Arrowheads (Michael Evans), Guidetaper, Pounch or Streamline (Guideline). Rio confuses the term a bit by calling their line with this taper WindCutter, which serves to illustrate that these lines are considered suitable for wind by some casters.

Long Belly
Long belly: these lines have extra long bellies, but are in other respects much alike the WF lines. Sometimes they have a longer rear taper. This has an effect when these lines are used on two hand rods, which is the main purpose of this type of line. A long belly line will act much as a DT line while you work it out, but still be able to shoot line in the cast.
Typical product names are Long Belly, Speycaster Taper, Steelhead Taper and Salmon Taper.

Short Belly
Short belly: this line has a short belly and concentrates the weight in the absolute front of the line - often with a short and steep rear taper. These lines will give a good casting power but without the hammer effect of the wind tapers. They are specifically designed for heavier fishing with larger flies and are often referred to as Bass Taper, Muskie Taper or Pike Taper.

Shooting Taper
Shooting Taper is also referred to as a Shooting Head. This line is just the belly part of the fly line with no running line attached. The running line is a separate line, which can be chosen freely by the angler. Shooting heads are chosen for effortless casting, distance and more flexible combination of belly and running line. Many anglers produce their own shooting heads.

Weight and density

The weight and density of the fly line is as important as its shape when it comes to determining its casting and fishing abilities. They might seem to be two sides of the same, but are not.

Even though lines are expensive, most fly fishers need a fairly good selection of different weights, tapers and densities.
Martin Joergensen

Weight: particularly the weight of the belly part of the line is critical for its performance on a certain rod. Line and rod has to work together. The AFTM-system used to describe weights of fly lines, specifies the weight of the front 30 feet of line. I will only make one further remark in that regard: never trust this classification! Use common sense, a scale and casting tests to select a line for a specific rod.

Density: the density determines the line's ability to float - or not to: its sinking rate if it is more dense than water. We usually talk about floating lines and different grades of sinking lines, ranging from neutral over intermediate to sinking and fast sinking.

The floaters are not just floating, even though you might think so. Some lines actually float higher than others, which influences the way the line lifts off the water and how thick the line is, hence heavily influencing its aerodynamic character. Thin lines are attractive because of their decreased wind resistance, but thinner means denser to attain the same weight per foot, and because of that the thin lines will not float as well.

The neutral lines equal water in density, while the sinking are more dense. And sinking is not only a question of using a denser material. Because the thick belly part is heavier per foot, it will sink faster than the lighter tip. This has urged some producers to make density compensated lines, where the tip becomes gradually denser to fight its slow sinking tendency. The classical sink tip line is basically an overcompensated line of this type.
These lines come in still more advanced constructions, such as high floating lines with clear, sinking tips for real easily spooked fish like the tropical bonefish.

Core and coating

The fly line is usually constructed from two central elements: the core and the coating. The core creates the foundation for the thicker coating. Apart from that it forms the strong part of the line, because most of the coating materials are soft and will easily break when pulled.

Core: this is most often made from braided nylon, where many hundred thin nylon strands form a braided tube. The tube shape is used by many for creating loops directly on the line after having removed the coating. You see other types of cores, amongst these the monofilament, which is popular for the clear lines due to its own transparency. Some lines utilize a braid of finer mono lines, which form a hollow tube, but of a somewhat rougher character than the normal braid.
Lately we have seen cores from different other copolymers and gel spun lines - technologies known from spinning lines and tying threads. These lines are particularly numb and will stretch very little when pulled.

Coating: this is the main material of the line - what you see and what you touch. It also forms the major body of the line and determines its taper and thickness as well as its final density.
The coating is made from all kinds of PVC, vinyl, polyurethane or other plastic and polymeric materials. Creating the right coating is beyond any reasonable doubt a complex process, and most manufacturers will guard the specific nature and formulas of their materials.
The manufacturers use a host of different materials and vary their density to obtain different floating and sinking abilities in the lines. This is typically done by incorporating lighter or heavier materials in the line.

The techniques are many from small air bubbles to air chambers for floating lines to different kinds of minerals and metals to make the line sink.
Furthermore the manufacturers vary the densities depending on the water the lines are to be fished in, taking into consideration the different densities of fresh, brackish and salt water. Things float higher and sink slower in saline water.

A good winter line falls softly even on cold days such as this in November
Martin Joergensen


Several factors influence the stiffness of the line: the material, the age of the line and the temperature of the surrounding media - both in the air and in the water.
You might think that as soft a line as possible would be the best thing in order to obtain delicate presentation, nice arcs and easy handling, but that is not the case. A soft line has a soft surface, and a soft surface sticks to the guides and yields a poor shooting ability. The soft line will also sag between the guides and further add to the friction.

That could lead to the belief that a stiffer and smoother line was better, but again there will be disadvantages. It will be harder to cast, unwilling to form proper arcs and unwilling change its shape in the cast. Apart from that the stiffer line will have more memory and keep its shape - usually curled from the reel - over time. And the smoothness could prevent you from getting a proper grip on the line.

In other words: a compromise between the two is the right choice.

The material is chosen to be fairly limp, but still have enough stamina to stay straight between the eyes and have a surface that is pleasing to handle, yet smooth enough to shoot well. Further smoothness is often obtained through a surface coating or treatment.

During the last few years the market has seen a new type of lines that are specifically targeted at fishing at certain temperatures. Many a flyfisher has been taken by surprise by a line, which during the summer was an absolute beauty, but on a cold winters day is like a piece of haywire - dead and impossible to cast. The low temperatures have simply made the material stiff.
Likewise, the tropical angler will wind up with a very soft and almost sticky line, if he uses an ordinary fly line on the deck of a boat under the scorching sun.

Because of this, we now see more and more cold water and warm water lines on the market, all suited for fishing under special weather conditions. A few manufacturers have so called all weather lines. Most of these are meant for temperate climate fishing: normal and cold weather, and not as suited for tropical fishing as the special lines for hot weather.

Some lines curl miserably in cold weather while tropical heat can make a standard line become sticky and extremely soft
Martin Joergensen


Most lines loose limpness and smoothness over the years. Materials deteriorate and the coating gets worn and dirty. This adds further to the inherent memory of the materials in the line and results in a line that becomes curly and stiff and hard to straighten.

Most fly fishers will nod in recognition to the picture of a line, curled up on the water like a clock spring. Especially after having pulled the line off the reel for the first time after an extended period of storing, like during a whole winter.

Some lines have very little of this memory while others have to be stretched into a proper shape every time they are pulled off the reel. Some will maintain their curled shape no matter how much you stretch. Their coating might be made from a material with a very good memory or they might be so old, that the softeners in the coating have disappeared or lost their softening capabilities.

Fly line care

The most important way to care for your line is to wash or wipe it off after each trip. Dirt, salt and all kinds of strange substances can stick to the line and deteriorate its surface and in the long run the coating and core.

Drag the line through a cloth soaked in line cleaner or just dunk it in a kitchen sink with lukewarm water and some mild detergent. Wipe it with a clean cloth and viola! Your line is almost as new.

You might consider wiping it lightly over with one of the many line dressings on the market. Be careful with car vinyl treatment products such as Armorall. It will work well on some lines, but most lines need to be treated with a substance based on silicone, and the wrong liquid can cause a lot of damage to the line. Read the manufacturer's instructions and consider buying the treatment particularly made for the line. Lines are expensive, and there is no need to ruin them while trying to make them better.

When you have the line off the reel, do not neglect to stretch it. The ideal stretch is to hang the line from a ledge and have a weight of 2-3 lbs. pull it. This will enable the line to untwist and stretch at the same time.
If you - like me - don't live in a skyscraper or have a 100' tower in the back yard, you might stretch the line between two posts or trees. I have a couple of hooks - one in each end of my house, and I drape the line between them in a couple of turns. Then I pull the line tight and leave the reel as a stretching weight.
Leave it for an hour or two. Wipe it off and treat it while it is there anyway, and then spool it back on the reel.
You can also stretch the line "in stages". Grab a piece of line firmly in your hands and stretch it by pulling it hard, move one hand the the center of the piece you just stretched and the other one an equal distance onto the yet unstretched line and repeat. Work your way through the full length of the line, maybe even twice. Curled line become significantly straighter after this treatment.

Most lines become as new after a wipe, a stretch and maybe a treatment with line conditioner.

Click here for other GFF articles that might interest you if this one was interesting

Slik lines

When granddad was a small boy a fly line was made from silk. There are still manufacturers on the market who produce silk lines. Silk lines have some highly praised handling and casting qualities and usually have a small diameter too. They are braided from a large number of silk strands and treated to float or slightly sink with a wax or a wax like substance.

Silk is a natural material, and silk lines need more care than modern lines. They are also quite expensive because of the amount of manual labor that goes into producing them.

There is only a couple of manufacturers of these lines in the world, but a lot of older silk lines are probably stashed away on addicts and in basements around the globe.
Phoenix Lines
JP Thebault Silk Lines


Great information on...

Great information on fly line, well simplify .
All people mention to match your rod with the line number it is recommanded.
If your want try this experience use a Line below and one number up, or that specify
Nimber, you may find solutions to wind condition, charge early your distance on small
River , try it, with today avaibility of type of line, it -  plus to try
Good fishing

Excellent article, t...

Excellent article, thank you. Ive directed a few new folks here, easier than trying to explain all the different types of lines and tapers.

also, something should be done about those dang addicts hoarding all the expensive silk fly lines. I hope they dont smoke 'em all. Meanwhile, searching through grandmas attic, I found some old reels of my gramps.

As a long time fly f...

As a long time fly fisherman (With a substantial break for the better part of 15 years), I'm now no longer a teen and am looking closer in to the science, purpose and specifics of various fly lines. Back in the late 80's Atlantic salmon and brook trout, primarily in rivers, were the name of the game where I lived. The only tapers I remember ever using were a standard DT, WF and I think I had something called a rocket taper (Probably similar to a wind taper). These days living in a different part of the country, the game has changed on me and it's all about northern pike, walleye and rainbow trout...bigger/heavier flies, colder climate/water and the biggest adjustment I'm finding, is standing water...and pike have teeth...BIG teeth. LOL This was a concise article with a great deal of a information packed in to it. Thanks.

I ended up buying an Orvis Streamer Stripper Fly Line as a first line for my pike setup, which is still in the mail at the time of this writing, but I can't wait to try it. I'm still in need of a double taper line for this rig, as I will often be fishing from a boat and won't need as much distance, but at $75, or more, lines aren't as cheap as they were 25 years ago. :D

Thanks again...great site, consider yourself bookmarked.

im a 1st timer what ...

im a 1st timer what line goes on the rod 1st the green rubber 1 or the rope one

TKS yo...

TKS you, i do like to overpower my rod.
My guess is that if the long belly has a belly 40 to 50% longer than a usual WF
it means you will have serious problems loading a rod with 9 meters line off the rod tip.
In softer tip rods that would be good with short casts and presentation will work almost like a double tapper would.
But with harder rod tips, i think it would be a bit difficult to load the rod for a shoot cast. wouldn' it ?!?!

Martin Joergensen's picture

Blatt, I like ove...


I like overlining my own rods a bit (personal taste), but apart from that recommend beginners to do the same because they rarely have a full belly out when blind casting, and because of this only rarely load the rod fully.

Whether to overline in particular when using a longbelly line...? I honestly can't answer you there. Personally I would probably do it, but again, that's how I prefer it.


Many guesses here......

Many guesses here...When using a long belly fly line, would it be a good idea to overline the rod?

Martin Joergensen's picture

TVK, A special li...


A special line... Heh! Many anglers actually use plain floss - almost any floss will do, even dental floss as long as the breaking strength is good enough. You can also find special floss made for the purpose, often just called "dapping floss".

The method is mostly referred to as dapping or blowline fishing, and you should be able to find references to that on the web and if you combine that with the name of author Robert H. Boyle you will most likely find his book on the subject.


Years ago, I saw an ...

Years ago, I saw an outdoor fishing show that featured a flat English flyline. The fisherman would put his back to the wind hold his rod tip high, play out line that would float in the air do to the line's 'wing-like' cross section. The gent would then lower his rod to allow a dry fly to lightly touch the water. He'd then raise the rod tip and repeat the process....dipping and skidding the fly across the water's surface. I think the process was called "doodling". I cannot find this special fly line. It would be dandy to use on the upper Platte River on windy days here in Colorado. Anyone know if this string is still available?

Am looking for the g...

Am looking for the grain of the line to match the wt. for reference. A 6 wt. is about 160 grain. What is the grain of the other reference wt.'s.? What wt. is a 330 grain line?

What are the 2 most ...

What are the 2 most important considerations in selecting a particular line weight?


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