The Chernobyl CFO (or "CFO Chernobyl Ant") is a high-floating, foam-based attractor dry fly, often used as a stonefly or hopper imitation in trout fishing, particularly in Montana and Wyoming. It is characterized by its large, buoyant, multi-colored foam body (often featuring bright colors like purple, black/orange, or flesh) and rubber legs that provide movement to attract fish.