"Non-tarnishing copper wire used for ribbing, weight, flash, wire bodies and dubbing brushes. XS: is the size to choose for ribbing on size 20 or smaller. Small: is an all-purpose size capable of filling many fly tying needs. Brassie: is an ideal choice for wire bodied flies sizes 18-22 and for ribbing on most trout sized flies. Medium: is a good choice for ribbing on size 8-12 nymphs. Large: is a popular choice for streamers and/or large stonefly nymph patterns."