The original Micro Mayfly in Olive, a Baetis imitation, has proven to be one of the best selling small mayfly nymphs of all time, and many will not head to the stream without it. Perhaps one of the best small nymphs since the Pheasant Tail. The larger copper bead size is tied with its recognizable chunky thorax; the smaller glass bead variation is much slimmer to imitate any black mayfly, such as a Trico, or tiny midges.