Gibson Power Tip Clamp On Marine Mufflers, 4 - in. inlet, 6.75 - in. overall. Tested with minimal or no power loss. High quality, Stainless construction. OEM style transom or clamp on mount. Utilizes water to dampen the sound. Easy bolt - 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.