Vertiflo jig style Craw fly.
Designed to slowly descend vertically and stand upright in a defensive posture when reaching the bottom.  Once reaching bottom, the fly should be retrieved either slowly or quickly with short pauses, where the fly can return to its vertical / defensive position.
#4 - 3 1/4” body length 
Tip:
For proper fly action, customers should work air out and fully saturate materials before casting.  Holding the fly below the surface and squeezing it a couple of times (like a sponge) will speed up the saturation process.