These can be used as tails on woolly buggers, streamers and a number of bass, pike and saltwater fly patterns or legs on frog patterns.
A major breakthrough on the use of the these was developed by Bob Popavics. He came up with the idea of attaching a 30 lb. monofilament line to the base of the tail using Zap-A-Gap glue. He then tied the mono line onto the shank of the hook. This has lead to these significant developments... Longer fly life. The monofilament will flex during the cast reducing the stress on the tail. If the tail does break off, you can glue a new one to the monofilament. A reusable fly. Finally, by using longer mono you can make extended body flies.
The first color is the "Flexi" material and the second color is the Holographic Speck.