These highly polished 316L stainless steel silencers are designed for the power boater looking for the simplicity of simple slide-on and clamp style installation and removal These silencers share all of the Cyclone's exclusive construction features and are available in 4 specific sizes for horsepower ratings; 1) up to 425HP, 2) up to 500HP, 3) rating above 650 By matching the horsepower specifications, you can obtain the perfect balance of a broad power-band with reduced noise Sold in pairs.