Fly lines range from the very thinnest and lightest for making short casts with tiny flies with tiny rods on small water, up to the heaviest, thickest fly lines designed to cast over-foot-long, massive flies with powerful big-game fly rods to catch giant fish in the ocean. All fly lines are numbered, on a universally accepted scale, by the physical weight of the first 30 feet of the forward, delivery end of the fly line; the bigger the number, the heavier the fly line. Fly rods are numbered in the same way,