Extremely effective in reducing engine exhaust noise and preventing water from returning to the engine. High strength design provides a significant safety margin over other existing fiberglass lift mufflers. For Gas/Diesel fuel type inboards, sailboats & generator applications. Sound rating: Better. Use above or below the waterline. Exceeds ABYC specifications. A1 2.0 A2 2.0 B 2.5 D 10.04 E 6.5 F 2.0