The Copper John is one of the best go to nymphs ever made. A must-have and is in most flyfisherman's boxes. Created by John Barr in the 90s to mimic the mayfly nymphs. With bead head, lead weight and wire it will get down quick in fast moving water. A great time to use it is during a mayfly hatch. But it works great anytime almost anywhere. It can be used as a double dropper under an indicator or by itself under an indicator. A real popular way to use this name is called the hopper copper. This is when you use a hopper as a dry like Roo's Hopper and use a Copper John as your dropper. 4X through 6x tapered leader and tippet are really great choices.