FMF Racing Factory 4.1 RCT Slip-On - Aluminum Muffler - Stainless Midpipe - Stainless Endcap , Material: Aluminum 043320 All new incorporating the latest in Resonance Chamber Technology Patented core shape lowers sound level while maintaining maximum power output Patented canister shape increases internal volume for more sound absorbing material Patented chamber design to enhance and refine exhaust pressure Factory Forward Engineering centralizes mass and is less prone to crash damage