Yoshimura RS4 Race Exhaust System Kawasaki Ninja 650 Features The Yoshimura Rs-4S features a Polyresonant duplex chamber, a two-staged stepped baffle, and an innovative carbon fiber turn-out end-cap Pentagonal-shaped sleeve Front muffler cap functions as a polyresonant chamber which helps reduce noise Two-stage stepped baffle Turn-out carbon fiber end-cap Stainless steel tail-pipe