“What fly line should I buy?”

Now, that’s the wrong question to ask.

“What fly line do I need?” – is a much better question.

This a recurrent question we all get personally, or it appears on some chat site. There is really no correct answer to this question. However, the chat sites immediately fill with – “I just got line x, and it is wonderful, can’t go wrong with that.” And more in that vein, lots more. The answers and advice are all given in the spirit of generosity and are undoubtedly well-meant. But this question can’t/shouldn’t be answered, until you have an idea about the intended use of said fly line.

Choose a line for the fish species?

Ok, so now you think the choice of line revolves around the fish pursued. That would be wrong, too.

The mass of the fly to use dictates the line choice!

There it is – once again and we come back to mass. But think about it a bit. How can it be any otherwise? Mass moves mass, and therefore the line’s mass must match the flies mass. The correct way to go about this, is to visualize the flies to be cast. Not their colors or shape, but their mass (and drag, too).


Let’s assume that the prospective buyer is a novice to trout fishing, and she/he loves casting weighted Wooly Buggers and Streamers. However, on the advice of well meaning anglers (or pranksters) an Amplitude Trout is purchased. The reason I use SA’s lines is that they are the industry’s leaders, and their lines are the best I can get for my needs.

Amplitude Trout line
Amplitude Trout line

This line is absolutely fantastic, but not for Streamers. Why not? The forward taper is 12-foot long, and hence there isn’t enough power in that head to turn over a heavy Streamer. So, now we have recommended a fantastic line for smaller flies, but the angler wants to cast big and heavy. That’s not a good situation to be in if the advice is heeded. Pay attention the the Trout’s long rear taper. This line can easily be cast far. So, what is a good line for an angler casting streamers. My advice would be the Amplitude Anadro line.

Amplitude Anadro line
Amplitude Anadro line

The Anadro has a short front taper (2-3′), and that means it will turn over hard, and it has the power to carry a heavy Streamer. On top of that, the Anadro is 1.5 sizes overweighted, meaning that a #7 Anadro weighs between a #8 and a #9 line. That will ensure plenty of power to turn over heavy flies. The Anadro excels at long distance casting and that is evident by looking at the long back taper. The reason that lines are not true to their line designation is that rods have become so stiff that only elite casters can bend/load them with the designated line. Intermediate casters must have more mass (line size up) to bend the rod. The line makers know this and have responded accordingly.

The second question I ask is how far can you cast or how far do you need to cast? Let’s now imagine that our angler is casting light flies in a small stream. The Amplitude Trout would easily work for that job. Of course, there are other lines that could work, too. For instance, Amplitude MPX or Amplitude Double Taper. What about light flies in a big river? The Amplitude Trout would be perfect in that situation because of the long back taper making long casts a breeze. Heavy Streamers on heavy lines banged down are probably not a good idea in a small stream. But they are absolutely an excellent idea in big rivers. Pay attention to the Anadro’s long rear taper of 30′. To be able to make long casts, this is the best taper configuration to accomplish that.


Bonefish are notoriously wary customers. Something big and heavy landing on top of them guarantees that they bolt, and fast. So, we use a line that we can lay down gently. Because of the usual wind on the salt flats we need rods #7-9 to be in the game. The flies we use could easily be cast with something smaller, for instance #4, but the wind would kill us. This is a good example of the necessity of using tackle to cast a light fly. This is frequently done too, when casting small flies to big salmon. When I have gone fishing for bonefish, I make a beeline for my Amplitude Bonefish lines.

Amplitude Bonefish line
Amplitude Bonefish line

Generally, when fishing in the salt you are use something big and heavy. Therefore, you need a line with some serious punch. Or in other words, a line with a very short front taper. The Amplitude Infinity Saltwater is a good all round choice.

Amplitude Infinity Saltwater
Amplitude Infinity Saltwater

If you still need more power to turn over some monstrous fly, there is the Amplitude Tropical Titan. Here, a lot of the head’s mass is pushed forward, and this baby will turn over hard.

Amplitude Tropical Titan
Amplitude Tropical Titan

First choose the fly – then the line

Now, the process of choosing the tackle is obviously going to start with the fly. First you must have an idea of the weight/mass of your intended flies to be cast. Ok, so now when we have that clear, we can choose the line that has the physical parameters to be able to cast the chosen flies. Remember, heavy lines can cast both light and heavy flies, whereas light lines can cast light flies, but struggle or can’t deliver heavy ones. There are only two parameters of the fly that influence its castability. Firstly, there is its mass, and secondly, the air resistance or drag.

Now lastly the rod is chosen

Now when you have chosen the line size that can handle the job, it is easy to pick a rod that can handle that line. Now remember the marketing in our sport is pervasive. Anglers have been led to believe that they need a trout rod, then a salmon rod, and my God don’t forget the saltwater rod. This is utter nonsense. The rod is a piece of graphite, handle and rod guides. It bends, then straightens and can easily break. It is dumb as a brick and an inanimate object. I use my #8 NRX Loomis to cast certain weight flies, and I happily use that rod for all fish likely to take those flies. A heavy line and heavy rod, can deal with a heavy fly, and also a light fly. The converse does not work. So, don’t show up under gunned.

It is important to know that there is no objective parameter to adhere to when a rod is made. After a rod is made, it is cast by some expert with various line weights, and then the expert decrees, “this is henceforth a #7 rod.” I repeat, no standardized objective measure decides the rod ratings. This newly minted #7 rod obviously casts best with a seven line, if you are the expert. It might work best for you with an “8 line, and some would like better to cast it with a #6 line. All fly rods can cast several line ratings, there is nothing mysterious about that, and it is perfectly fine to use the line weight you like. So, all this writing about the crime of underlining or over-lining is a bit misleading. It is your rod and your line, and just use it as you like best. You have my blessing.

English consultant: My good retired neighbor Joe

Technical consultant: Bruce Richards