That said, one aspect of fly lines always in plain sight is taper design. Fly lines are different than the monofilament, braid, or fluorocarbon used with conventional tackle in that they're weighted. The weight of the line is what the angler leverages to hurl a very light fly, and the weight rating of a line, in general, is meant to correspond with the size rod it's paired with. But where that weight is distributed in a line can make a huge difference when it comes to casting and fishing. For example, a line with all its weight packed near the front is going to generate energy to chuck flies, but a distance caster is going to want some weight reserved for the middle section, otherwise you'll have to strip in all the belly, and then shoot on every cast to generate any length. Mending is critically important to an effective presentation, and some lines mend better than others. Again, if all the weight is bunched up like a bullet in the front of the line, and all you have to lift and move is running line, you won't be able to mend as effectively as you would with some weight distributed farther back. If I'm turning over big streamers and making repeat casts at moderate or short distances (like banging the banks from a drift boat), I want that weight packed up front so I can lift and fire at will. On the other hand, double-tapers work well for dry-fly fishing with rods that are 4-weights or lighter, in particular. For most fiberglass rods, I still like weight-forward lines, but that's just me.