Many of the recipes in this booklet mention Zelon dubbing in the ingredients.  The more I use it, the more I like it.  Each package contains a perfectly blended color – many for specific species, as well as the correct mix of natural & synthetic materials for the proper texture and buoyancy – that is spiky sinking material for nymphs and finer floating materials for dry flies.  Their “Pheasant Tail” is a great substitutes for the naturals and their Caddis colors are outstanding.  Try em – you might like em.  If you’re interested – check them out at BlueRibbonFlies.com or drop by the next time you’re in West Yellowstone, Montana