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. Features: Available in Blue Anodized Titanium 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. Fitment: GAS GAS EC250F 2021 GAS GAS EC350F 2021 HUSQVARNA FE250 2020-2021 HUSQVARNA FE350 2020-2021 HUSQVARNA FE350 ROCKSTAR EDITION 2021 HUSQVARNA FE450 2020-2021 HUSQVARNA FE501 2020-2021 KTM 350 XCF-W 2020-2021 KTM 450 XCF-W 2020-2021 KTM 500 XCF-W 2020-2021