The small BK438 is ideal for placing wire wraps near the head of the fly. Its stainless steel tube guides the wire from the spool to the attachment point. The guide rings protect the thread from fraying during winding. Compared to the larger BK457, choose this size based on the distance you prefer to keep between your hand and the hook. A clean finish, free of wax or dried varnish, remains essential when working with fine threads.