FMF Racing Factory 4.1 RCT Slip-On - Aluminum Muffler - Stainless Midpipe - Carbon Endcap , Material: Aluminum 042291 Incorporating 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