Yoshimura poured endless man hours into the development of the RS-4 silencer...This commitment finally payed dividens in 2010 when it won the AMA 450 Supercross and Motocross Championship series, and again in 2012 by winning both 250 Supercross Lites titles. That same R&D has now been directed to developing the current generation RS-4 exhaust for Road Racing.The RS4 features a Polyresonant duplex chamber, a two-staged stepped baffle, it's unique design provides an unrivaled combination of power and a quiet exhaust note. The pentagonal shaped muffler provides a great visual look that complements the look of any sports bike, finsihed off with an innovative carbon cone end cap.