Developed in conjunction with AMA Pro Supercross / Motocross teams, this evolutionary exhaust system combines power, light weight, and centralized mass to give you the confidence to dominate the race track. The RS-4 is a unique design with predicated power, a side benefit of a quiet earthy exhaust note that speaks volumes for performance and offers increased horsepower and torque. The 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 bike's components. It features a polyresonant duplex chamber, a two-staged stepped baffle and an innovative carbon cone end-cap. 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 tapered header and mid-pipe. Considerable weight reduction.