Wapsi Thin Skin is .004″ thick and can be used on flies past size 18. It is stretchable and transluscent with a matte finish on one side and a shiny finish on the other. The backing makes it easy to cut to width. Wapsi Thin Skin MottledOak is the best part of a Grade #1 mottled oak turkey quill reproduced on thin skin. Best for wing cases on big stone flies and shell backs on crawfish.