The Micro Balanced Bung Damsel Nymph is a great looking "whispy" sparsely tied damsel imitation. The term Bung is in reference to the stillwater strike indicator some use in conjunction with this fly. The two options in this product listing indicate two different weights of fly and two corresponding visible colors on your "bung" indicator. You can fish this pattern as you would a balanced fly or strip it slowly with a floating or clear intermediate line.
For more info on the bung indicator check out the video in this listing.