The Factory 4.1 RCT incorporates the latest in FMF Resonance Chamber Technology both internally and externally. In addition, we achieve a shorter overall length that is less susceptible to crash damage and complementary to our Factory Forward Engineering - moving the muffler closer to the motor to centralize mass. The Factory 4.1 RCT is constructed from only aerospace grade materials that meet our exacting specifications and is manufactured 100% at our Southern California factory. -Available in Natural Aluminum Muffler with Carbon End Cap -Massive Power gains throughout the RPM range. -Huge weight savings -New RTS (Rapid Tuning System) -FMF uses the highest quality proprietary blend of alloy grade titanium made especially to our standards. Make Model Year YAMAHA WR250F 23-24 YAMAHA YZ250F 19-24 YAMAHA YZ250FX 20-24 Fits: Yamaha YZ250F 2019-2021 YZ250FX 2020-2021