Gibson Power Curves Turndown Clamp On Tip,4 - in. Inlet, 12 in. overall. Tested up to 1200HP with minimal or no power loss. High quality, Stainless construction. Utilizes water to dampen the sound. These silencers were specifically designed for Large displacement motors such as 500HP, 502, 525, 525SC, 575. and up to 1,200hp. Easy clamp - on installation. The Gibson Marine Mufflers have proven to reduce decibel ranges within and to surpass the 88db limits required by the California SAE J2005 Motorboat Sound Law without compromising power.