Pro-Flow mufflers utilize DMP's proven Hi-Helix muffler core design. These muffler tips are rated for applications up to 425HP. They offer maximum noise reduction while not hurting your engine's performance. The exclusively designed Vortex variable flapper will allow your engine to breath in high RPM situations yet keep your boat within strict noise regulations. All stainless steel construction, includes external clamp-on flappers. 7" long, 2" outside and 5" inside. Sold in pairs.