These are flies used after dark, in deep water, or where visibility is not very good. The large bead-chain eyes and the bulky dressing, create underwater vibration. The bead-chain eyes make the fly dip every time the angler pauses on the retrieve. This gives the fly a jigging motion on the retrieve. It was developed by American West Coast Fly fisherman Dan Blanton. The large wing and bulky body generate sound waves in low-visibility water so tarpon and other species can find it.