CDC Dun Black #18

A CDC-tied mayfly dun in black from RIO. CDC (cul de canard) feathers trap tiny air bubbles for natural buoyancy, giving this pattern a soft, lifelike footprint on the water.

At #18 it suits small dark mayflies and midges. Fish it on a dead drift, and refresh the CDC with desiccant or false casts to keep it floating.

On flat, glassy water, lengthen your leader and downsize your tippet selective trout notice everything except a perfectly presented mayfly.