Aluminum Stabilizer and Ski Boat Fin - Improves performance in any I/O or outboard motor! - The Whale Tail XLr extends out behind the prop to utilize prop wash energy which is normally lost. Whale Tail transforms this energy into lift for immediate response when the throttle is applied. Unique hydrodynamic design Stabilizes bow-light boats Pops skiers up in less time - Flattens wake for water skiing; creates positive, skid-free turns With bow lowered, visibility is improved-and safety Smooths out ride in rough water Reduces porpoising & cavitating Increases top speed and fuel savings in most applications Mounts on the anti-cavitation plate of all inboard/outboards and outboards Installs in 15 minutes with stainless steel hardware included