EP Trigger Point Int'l Fibers can be used for tying dry flies the same way you would use standard polypropylene. Fibers are a bit softer and finer compared to traditional polypropylene materials. These fibers have been designed to match a multitude of wing and body colors found in insects world wide. All colors have been treated with Water Shed waterproofing liquid. You can use this product from insect imitations to large salmon dry flies.