A Guide to Choosing Fly Lines

When I started fly fishing there were two or three fly line brands available, and maybe one or fly lies from each to choose from.  My first set up was bought at a local angling shop, and it came with a line that I was told would be “easier to cast”.  It was a green Cortland line, and, to my shock, it cost as much as the rod and reel.  On reflection it was a good quality line that lasted a few seasons and it worked well on my 6/7 fly rod which was horrible and cheap.

In researching this article, I checked the major manufactures web sites, and one of them had over fifty freshwater fly lines to choose from. For the beginner (and some seasoned anglers as well) it would be a nightmare to make a choice from these.  Hopefully this article will guide you in your next line selection.


Before the 1950s, and the invention of plastics, fly lines were made of horsehair, or silk. Silk lines were expensive, didn’t float without the aid of grease, and tended to get waterlogged after a few hours of fishing. They required a lot of maintenance, and at the end of the day they needed to be dried carefully before storing, otherwise mould and mildew would develop and quickly ruin them.

Now fly lines are made from a fibre core with a PVC coating and are relatively cheap. The fibre core provides strength, and the PVC coating provides weight, and the appropriate density to make it float or sink as required.  They float extremely well and require little or no maintenance (other than a wash in warm water and wipe down every now then).

How are lines classified

Lines are designated by 3 variables, their taper type, their weight, and their buoyancy. (e.g. WF3F => Weight Forward, 3 Weight, Floating line).  Let’s look at these in reverse order.

Line Buoyancy

Lines are generally classified by their buoyancy.

Floating(F) Lines:  these clearly float on the surface of the water, and are used to fish flies within a few metres of the surface

Intermediate(I) Lines – are used to fish within a few metres of the surface also, but are better than floating lines, where there is a lot of wave or chop. (you get a much straighter connection to the fly, whereas a floating line will go up and down the waves). Wind also doesn’t cause an intermediate line to drift as much.

Sinking(S) Lines: These are typically used in fast or deep water, where you want to have you fly descend quickly or deeply.  Usually used from a boat in deeper parts of lakes and ocean. 

Line Weight

Lines come in different weights to match the different rods we could use.  We normally select the rod according to what we fish for.  You can imagine we need a much stronger rod to catch a Tuna in the sea, than we would to catch a trout in a mountain creek. The stronger the rod, the more it takes to bend it, and the higher the line weight we would use, hence rods are classified ideal line weight they are designed to cast.

In 1959, to standardise the industry, the AFTMA (American Fishing Tackle Manufacturers Association) created a standard for fly lines, and by de-facto for rods.  Coincidentally this was around the time when the modern PVC lines were first introduced. The AFTMA classification bases the line weight on the first 30 feet of line, and it must weigh within the specified range to meet the standard.

AFTM numberIn grains (range)In grams
3100 +/- 66.48
4120 +/- 67.78
5140 +/- 69.07
6160 +/- 810.42
7185 +/- 811.99
8210 +/- 813.61
9240 +/- 1015.55
10280 +/- 1018.14
11330 +/- 1221.38
12380 +/- 1224.62

This was meant to help standardise the industry.  The idea being that a 5wt rod (for example) would be made to cast a range of weights, but have sweet spot at 140 grains of weight, thus allowing you to cast from one to sixty feet of line.  Rods can easily cast a range of line weights effectively: easily one weight heavier, or one weight lighter. This is called over and under lining a rod. Notionally a 5 wt., for example can reasonably cast a 4wt through to a 6wt line.  overlining a rod will make it feel softer, underlining will make it feel stiffer.  If fishing a lot at short range, we might overline a rod to move it into the sweet spot, or if casting a lot at a distance we might underline a rod.

Line Taper Type

All fly lines have a taper at the fishing end of the line (front taper), where the line tapers from its thick mid-section(body) down to a millimetre or two thickness at its front end (where the leader is tied on).  This front taper is designed to help turn over and straighten the leader on the presentation cast.  Beyond this there are many ways for the remaining line to be tapered to change its casting characteristics.  By altering the taper design, manufacturers create many diverse lines with different casting properties. There are four classes of taper designs:

  1. (WF) Weight Forward,
  2. (DT) Double Taper,
  3. (T/Spey) Triangular Taper and,
  4. (L) Level

Weight Forward (WF) lines are now the most commonly sold tapers.  The WF Taper design was created to help cast longer distances. A weight forward line has two main segments, the Head (the thick weighted part at the front of the line) and the running line (thinner lighter part which is joined to the backing on the reel). 

The head of a traditional WF line is made up of three parts, the front taper, the body and the back taper (where the line thins down and becomes the running line).  The weight forward line design allows manufactures to have multiple front and back tapers to change how the weight is distributed through the head section. Using these they and can move weight closer to, or further away from, the leader end of the fly line.  Of recent times they have been moving weight forward to help add weight to front half of the line to make it easier to cast shorter distances, but this comes at a cost. For example, by moving the weight forward, it reduces the weight at back of the head, this makes it harder to roll cast and mend.

The Head (generally about 30ft long) carries the weight that is used to cast the rest of the line.  For a distance cast, the angler false casts to extend the head of the line just beyond the rod tip and the thin running line is still within the rod rings, then the final delivery cast is used to shoot the running line. The running line being thinner and lighter has less weight and friction enabling the head to be cast further.

With weight forward lines, false casting, is limited to the length of the fly line head, as the line will hinge and destabilise the loop if you try to false cast with any of the running line beyond the rod tip.

For most of the modern WF taper designs, they cast well in close.  However, a WF with a long front taper design may not have as much weight to load the rod on shorter casts and may be difficult to cast well. Especially for the beginner.

Most weight forward taper designs are generally not great to roll cast, as the weight is too far forward and can be difficult and even unbalanced when trying to roll cast beyond 20 or 30 ft. Similarly, WF lines, can be more difficult to mend, as there isn’t enough weight close to the rod tip to help move the heavier front section.

Double Taper (DT) lines were once the norm, being the traditional design for early PVC lines as they were quite easy to manufacture.  A Double Taper line tapers from a thin tip to a thick body, which runs the length of the line, and then it tapers down to a thin point at the rear. The fly line is symmetrical and really doesn’t have a front or back and in-fact can be turned around, when the end tied to the leader becomes worn or cracked. This effectively gives you double the life of a WF.

When distance casting a DT line, the body has more weight and friction than a WF running line, so it can’t be shot as far.  Hence to cast a long distance with A DT, the caster needs to aerialise more line during the false casting phase than they would with a WF line.  How far an angler can false cast a DT is limited by their ability and timing, and a competent caster to cast one just as far as a WF.

Casting a DT line for short casts presents no real difficulty, the DT is true to weight so will load the tip of a matching rod weight properly. Having the weight distributed evenly through its length, makes it easier to roll cast than a WF, especially at longer distances. DT lines are also easier to mend than WF lines due to the even weight distribution.

Triangular/Spey Taper. (T/Spey)

Spey casting,developed for Salmon fishing and named after the Spey river, is a style of casting that is based on variations of the Roll Cast. Spey/Triangular taper lines have a thin running line, and a triangular shaped head section. From the running line, there is a short back taper to the line’s thickest part, then the line has a long front taper down to the front point. The Triangular  taper is 30 -40 ft long in general. This design has more weight closer to the rod tip, which maximises the efficiency of the energy transfer for roll casting.  Having more weight closer to the rod tip also makes mending easier.

For effective distance casting, the angler can begin with the head section just beyond the rod tip, and roll cast the whole head to generate enough speed to shoot all the running line.

Generally, a two-handed rod is used for Spey casting, and hence no overhead false casts are ever made.  However, some anglers use Switch rods, which can be used for both overhead casting and Spey casting, and as at times will false cast a Spey line.  As with a WF, the length of a Triangle taper line that can be false cast is limited to the length of the fly line head.  If you try to false cast with any of the running line beyond the rod tip the line will hinge and destabilise the loop.

The long taper means there is less weight in the front 15-20 feet, so a triangular taper doesn’t load a rod in close as well as a regular WF or DT line in the same weight class if an overhead short cast is attempted.  Despite this, making short roll casts is simple and easy due to the taper design. To improve longer range casting some triangle tapers are actually overweight (first 30 ft as per AFTMA rating) and are at least one weight heavier than the marked weight. Don’t be put off by this as this means the 4wt TT will suit a 4wt rod.

Level (L) Level lines are just like a Double Taper without the Tapered ends.  As level lines are only used for specialist applications, I have left them out of consideration here.

Comparison Chart

TaperDistance CastingShort CastsRoll CastMendingFalse Cast LengthOther
WFGood/Easier for BeginnersGood (Avoid LT design)Ok in closeOk in close.Limited to Head Length (30/40) ftSpecialty taper designs available
DTGood/Requires more skill for long distanceGoodGoodGoodLimited only by casting ability, whole line is technically possible.)Last twice as long
T/SpeyGreat/Skilled Spey casterGood for Roll castsWhole line, with shootingGreatLimited to Head Length (30/40) ftDesigned for roll casting.

Choose Line weight to suit the fishing

The line casts the fly, the rod casts the line and the angler casts the rod.   Think about what you will cast. If you are casting big bulky flies, heavy nymphs, double nymph rigs or nymphs and big indicators, you will struggle with anything under a 5 weight. If you are casting small flies, you can easily use a 2,3 or 4 weight line.  If you need a heavier rod, to manage the size of the fish you are chasing, you will need a heavier line to match the rod.

The marked rod weight is only a guide

The line weight marked on a rod is meant to be the line weight the rod was designed for, but (and it is a big Kardashian sized but) there is a problem with modern rod rating.  When I bought my first, fly rods were labelled with two line weights, mine was a 6/7.  It was understood, that if you were Lake fishing (distance casting) you would fish it with a 6 weight line, and if you were fishing a stream in close, the rod would perform better with a 7 weight line. The equivalent rod, if sold today, would probably be sold as a 6 weight.  As a result, line manufactures are now selling lines a half weight heaver, or with complex tapers that push weight forward to load the rod better in close.  Rather than worrying about a specialty line, you could easily do what I did 20 years ago and buy a line weight heavier. Buy a line that suits the rod and don’t be afraid to use your rod with more than one line weight, according to the situation.

Line Coatings, materials and textures

The major line companies invest in the design of the materials, textures and coatings to improve slickness and durability.  Textured lines apparently shoot better; however, they can be noisy and abrasive.  Slick coatings on lines are good when new but they do wear. There is no doubt that they do improve the slickness of lines, but not sufficiently to influence my line choice.


Comparing the main manufacturers, there is a difference in line durability.  I tend to fish quite a lot these days, and I do punish my fly lines. So I prefer lines that will last.  Cortland lines are very durable, and Scientific Anglers are a close second.  Rio had trouble with their coatings on some lines cracking and not lasting in the past, and they seem to have fixed these, however for me they still seem to wear quicker than the other two. Generally these lines are in the top bracket.

At the other end of the scale, you can pick up lines quite cheaply on the internet.  They come direct from one or two Chinese factories, and appear to be copies of the big manufacturers’ lines.  Mostly they are OK, but I have found the quality quite variable. Issues include line tapers being a bit off, cracking and deterioration of lines, and some lines not floating well.  If you aren’t fishing too often, you are just starting out, or you want a practice line it is hard to argue with the price of these, but you will need to replace them more often.

Final notes, advice and some personal opinions

Consider buying a good line from a good manufacturer, it will cast and last well. If you are trout fishing, buy a floating line, but consider an intermediate line as a second line if you are going to fish lakes regularly.

If you are fishing rivers or streams , when you do purchase the new line, there will be many WF lines to choose from, but think about buying a DT line; it won’t limit your casting, and your wallet will thank you. Buy the lines that match your fishing and your rod. Consider one line weight up, if you need help loading the rod in close, or want to cast heavy nymphs and big indicators.

If you are fishing lakes, and you need help achieving casting beyond 40ft, grab a true-to-weight WF line that matches your rod.  Overlining your rod for distance will not help.

You should now have enough information to help you select your new fly line, according to where and how you use it.  Good shopping and tight lines!


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: