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 with Carbon Fiber End Cap -Massive Power gains throughout the RPM range. -Huge weight savings -New RTS (Rapid Tuning System) -FMF uses the highest quality proprietary blend stainless steel made especially to our standards. Make Model Year GAS GAS EC350F 21 HUSQVARNA FE 350 20-23 HUSQVARNA FE 350 ROCKSTAR EDITION 21 KTM 350 XCF-W 20-22 Fits: Husqvarna FE 350 2023