Ice Dub by Hareline Dubbin;

Ice Dub is a Mylar-like substance that is able to reflect and refract light in a number of unusual ways. It is super sparkly which makes it very popular for tying nymphs and emergers. Can be used by itself or blended with other materials. In some colors it appears much like natural animal fibers. In other colors it adopts a UV halo much like several insect species. In still other colors Ice Dub has holographic properties like fish scales. Ice Dub is fine textured and fairly easy to tie with.