Many don’t know this, but the WD-40 was developed by Duranglers guide Mark Engler to represent emerging baetis on the Roaring Fork and the San Juan River tailwaters. Since its inception, the WD-40 fly pattern has become a fairly famous pattern that mimics hatching midges, BWOs, and even PMDs. The WD-40 also works great when fished with weight on the bottom. Heck it works pretty great no matter where you fish it in the water column. Put some floatant on it and fish it as a dry emerger for those picky tailwater risers.