Bronze Sproat Bend Straight-Eye 1X-Fine Wire 3X-Long Curved Uses: Swimming Nymphs, Leeches, San Juan Worms. Bronze, Sproat Bend, Straight-Eye, 1X-Fine Wire, 3X-Long Curved Shank, Forged. In the mid 1980's, Daiichi introduced this "swimming nymph" hook to form the foundation for swimming mayfly nymph artificials, and for flies imitating leeches or worms. The gentle "s" curve helps give a life like appearance to these creations.