How do you pick a fly rod? There's so many different lengths, types, styles, and prices. When you go into a fly shop and you see this huge rack of fly rods, how do you know which one is right for you? Well, the first thing you have to decide, believe it or not, is the line size. Unlike a different kind of rod like a spin rod or a bait casting rod, where you pick your rod and then decide within three or four different lines which line to put on it, the first thing you have to decide with fly fishing is what fly line do I need. The fly line is thick and heavy and it's relatively permanent; it's not disposable so you use this all the time. This is the stuff that makes the rod bend properly. This is also the stuff that allows you to throw certain size flies.
Fly line sizes determine how far you can cast, what type and size of fly you can throw, and what kind of fish you can land with that rod. The same fly line that will throw this great big heavy streamer, with a weighted head on it, is not the same fly line that's going to deliver this little tiny dry fly with delicacy. The one that throws this bigger fly is going to be thicker and heavier than the one that throws this little tiny dry fly. I can show you two different rods. I have a 4-weight here in my hands, which would be typical for a trout stream like this, and I have another rod here: a 9-weight, which would be your basic saltwater rod. Even from quite a distance, you can see that the line is thicker on the 9-weight rod and also the rod is much thicker. This rod has a lot more beef and a lot more guts. It can hold this heavy line in the air a lot better than this 4-weight. This 4-weight can't hold that 9-weight in the air at all. In fact, you might even break the 4-weight if you cast a long cast with this 9-weight. So, two different weights, the 4-weight has the delicacy to throw a trout fly and the 9-weight has the power to throw a big saltwater or salmon or a bass fly without collapsing.