Purchasing a trout leader isn’t always simple. You’ll have to figure out the length and diameter that you’re looking for, as well as the material that you want. At most fly shops, you’ll have two options: mono or fluoro. If you’re new to fly fishing, there’s probably no reason you’d know what either of those materials is – so here’s a little bit about both.

The “mono” in monofilament means that it’s made from a single strand of nylon. It floats well, stretches, and is softer than fluoro – allowing for delicate fly presentation. It’s also significantly less expensive than fluorocarbon.

Fluorocarbon trout leaders are designed to be stiff, abrasion-resistant, and quick-sinking. The underwater visibility of fluoro is also much lower than that of mono, and it’s generally stronger and more durable – hence the higher price tag.

A general rule for leader material: Any part of your leader that you want to float should be monofilament, and any part that you want to sink should be fluorocarbon.

For dry fly fishing, monofilament is the way to go. If you want your fly to float, you’d better be using a leader that floats – a monofilament leader will help you control your drift and present the fly in a way that looks natural.

For nymph or streamer fishing, go with fluorocarbon. Whether you’re fishing nymphs or streamers, you want your fly to sink quickly to the desired depth in the water column – fluoro will sink a whole lot faster than mono, and it will also hold up better to the beating offered by subsurface rocks and logs.