The RS-4 is a unique design with predicated power and a quiet earthy exhaust note that speaks volumes for performance. This RS-4 features all the benefits of the original RS-4 muffler, but with a unique turned-out end-cap, designed to direct exhaust heat and gases away from the bikes components. To top-it-off, they embossed Yoshimuras "347" logo in the carbon for a clean look. With all its benefits in mind, the RS-4 was an obvious choice for the WR450F. Aluminum pentagonal shaped muffler sleeve and aluminum mount bracket. Features a polyresonant duplex chamber, a two-staged stepped baffle, and an innovative carbon cone end cap. Durable high-grade stainless steel tail pipe. Considerable weight reduction. Carbon fiber end cap comes with a 94db U.S.F.S.-approved Spark Arrested insert installed in the muffler. Step-by-step directions and all necessary hardware included for an easy installation. Note: For closed course competition use only. Not intended for street use.