Behold the Tungsten Beadhead Nymph
Tungsten Beadhead nymphs are the speediest sinking beadhead fly of all, simply because the tungsten head weight of the fly is normally employed as the point fly on a team of flies. The weight ensures team goes down fast and assists in pushing and holding the team deeper. If you fish identical flies with and without beadheads to the same fly pattern, you can fish effectively at different depths and speeds.