This is one great fly with just two tying materials. One CdC feather and a pinch of deer hair.
Hans Weilenmann is in my opinion one of the best creators of flies in the world. I fish regularly with these patterns – especially this and the CdC & Elk Adult witch is a pattern that performs fantastic both during caddis and mayfly hatches.
The fly is made of just two different materials: One CdC feather and Deer Hair (no, not Elk). The second remarkable thing about it, is that the way the CdC is tied in, the barbules forms a shuck/trigger that really excites feeding fish.
I must admit that I was skeptical the first seasons I tried out these patterns. They are grey and rather dull looking dries. And, I did hear that during a normal mayfly hatch, when trout are just on average choosy, they perform great. And boy they do. The first year I fished them, they performed particularly well during the Aurivilli and Danica hatch (on size 12 and 10 hooks).