FMF Factory 4.1 RCT Fits 2025-2026 Kawasaki 250f incorporates the latest in FMF Resonance Chamber Technology both internally and externally. It starts at the center with a new core - a patent pending shape enhances and refines the exhaust pressure wave for optimal power output while lowering the sound level. In addition, it achieves a shorter overall length that is less susceptible to crash damage and complementary to the Factory Forward Engineering - moving the muffler(s) closer to the motor to centralize mass. Visible changes to the exterior include a redesigned canister to increase internal capacity for the maximum volume of packing material. The packing itself was not overlooked - a proprietary blend formulated for superior durability and sound attenuation. The final component is a new rear endcap engineered for simple tuning adjustments incorporating a snap ring feature to secure the standard and optional inserts. Massive POWER gains throughout the RPM range. Quieter than stock. Huge weight savings. Includes midpipe. Can be used with FMF header or stock. New RTS (Rapid Tuning System) makes for easy sound insert changes as well as adding U.S. Forestry Service Approved Spark Arrestor. #1 Exhaust in AMA Supercross Series, AMA Motocross Series, FIM Motocross of Nations and the Monster Energy Cup!