This particular artificial fly is designed to imitate a small aquatic insect nymph, specifically employing a heavily weighted, streamlined profile. The intent is to quickly sink through the water column and present the imitation to fish feeding near the bottom in fast-flowing currents. This design often features a smooth, epoxy or resin coating over a body constructed with materials like peacock herl, synthetic dubbing, and tungsten beads for weight.
Its effectiveness stems from its ability to rapidly reach the strike zone where trout and other fish often forage. The slender silhouette and dense construction contribute to reduced drag, allowing for a more natural drift presentation. This design is especially useful in challenging fishing conditions, such as high water, fast currents, or when fish are holding deep. Its popularity has grown due to its proven success in various fishing scenarios.