The Zika Collection.
I use this fly almost all year as my upper dropper on a multi fly French leader rig. It seems the rivers that I fish never run out of small black and white segmented midges and other larva that trout are on the lookout for.
Hands down, this is the single most effective fly in my box. My logs are beginning to show exceptional numbers of fish that this fly has been producing this year. I have not had a day later when I cannot draw a fish to take. I try to use other patterns, but this one always gets put back on.