The work that went into developing the RS-4 muffler has paid big dividends in Off-road Racing; winning multiple Supercross and Motocross titles since it's inception. We've developed the current generation RS-4 based on that research & development, and the result is a unique design that provides an unrivaled combination of power and quiet exhaust tone. The RS-4 features a Polyresonant duplex chamber and two-staged stepped baffle for increased performance, while a carbon cone end cap finishes off its innovative styling. Pentagonal-shaped sleeve Front muffler cap functions as a polyresonant chamber which helps reduce noise Two-stage stepped baffle Carbon fiber end-cap Stainless steel header and tail-pipe Repack Kits, optional Insertsand Spark Arrestersare available for all models