M4 Exhaust manufactures exhausts which add power and a more race-inspired sound to your bike as well as lowering the overall weight. Extra time on research and development ensures your exhaust has the ultimate in quality workmanship, ease of installation, and the best performance possible for your motorcycle. M4 Exhausts are available in both Standard / Race and GP Series mounting configurations. Step up your motorcycle's style and power with the M4 GP Series Full System Exhaust. Single stainless steel muffler, ceramic coated black. Saves 20 pounds over stock. Full systems include tapered and equal length headpipes with true high-flow merge collectors. Stage 2 quiet insert is optional (sold separately). Most systems are quiet insert compatible and, where applicable, are shipped with an O2 sensor bung for use with aftermarket fuel management systems.