The Bubble Back Micro Nymph - BWO (blue winged olive) imitates, among other mayfly nymphs, the ubiquitous baetis emerger. Fish this unweighted in the film for some great fly fishing action!
The Bubble Back Micro Nymph - BWO is particularly effective for the following Mayfly Hatches:
Very effective bug in quick/swift water, especially right when the hatch starts. I guide on the San Juan and have taken lots of nice fish on this pattern. Seems reasonably durable.