Fly fishing is an ancient, distinctive angling method, developed primarily for trout and now extended to other species. Artificial flies are constructed — "tied" — in sizes and colors to match naturally occurring insects or baitfish. Fly rods are relatively light and long, and are made in a variety of weights to match the size of the fish being hunted. Fly reels are manual and of a simple spool design to accommodate the fly line and backing. Fly lines are 20-30 meters long and are matched to the rod according to weight. Because the fly itself adds very little weight, the fly line must be heavy enough to flex the rod and carry the fly to the target. A leader of 2-3 meters is used between the fly line and the fly itself.