Superior power than stock systems. Available with titanium and stainless steel headers. FMF's Factory Forward Engineering centralizes mass and is less prone to crash damage. Innovative rear end cap features simple installation of tuning tip inserts or spark arrestor with the removal of four screws. Meet AMA and FIM sound requirements. QuietCore 94 dB insert included. Spark arrestor included in muffler.

Factory 4.1 muffler available in natural titanium or blue anodized titanium with titanium end caps. The lightest mufflers available. Superior power and performance - horsepower improved throughout the rpm range. Feature exclusive proprietary Chamber Core technology. Factory Forward Engineering centralizes mass, improves handling. Made from premium quality American materials. Customize with performance tuning inserts and spark arrestor module. Meet AMA sound requirements on most models; inserts available for others.