Davis Instruments Whale Tail XL Hydrofoil Stabilizer Improves out boat or I/o performance Reduces proposing and cavitation Increases fuel efficiency The Whale Tail XL extends out behind the prop to utilize the prop wash energy that normally is lost breaking the water. This energy is transformed to lift against the Whale Tail XL for immediate response when the throttle is applied Stabilizes bow-light boats. Adds safety - when bow is down, vision is improved Increases top speed and saves fuel in most applications Smoothes out ride in rough water; reduces porpoising and cavitation Made of marine grade aluminum with durable anodized finish. Installs in 15 minutes with stainless steel hardware included.