Want a fly that will catch fish? This is the one. It was developed on the San Juan River in New Mexico but it has found its way to be fished all over the world. What fish can resist a worm? I always carry at least 6 of these bad boys in my box in multiple colors. It is irresistible to many fish such as trout, bass, and pan fish. When you don't know what to fish tie one of this on as a top nymph or a bottom nymph. All San Juan Worms are tied on a size 14