Hook:

18 - 22 Tiemco 101 or other standard Straight Eye dry fly

Thread:

8/0 Uni-Thread Olive, Grey or Rust

Wing Case:

Grey closed cell foam loop

Tail:

Mayfly Brown straight zelon

Body:

BWO Olive Superfine, Beaver or Zelon Dubbing 

Hackle:

Light Dun clipped flush with hook point

This is a great fly to use just before a Baetis hatch.  Pretty hard to see this low-floating little bug, it works well as a dropper, fished behind something you can see like a larger Parachute or Cripple Adams.