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. -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 specifically to our standards. FITMENT: KTM 350 XCF-W 20-22 KTM 450 XCF-W 20-21,23 KTM 500 XCF-W 20-23 HUSQVARNA FE 350 20-23 HUSQVARNA FE 350 ROCKSTAR EDITION 21 HUSQVARNA FE 450 20-21,23 HUSQVARNA FE501 20-23 GAS GAS EC 250F 21 GAS GAS EC350F 21 Please ensure fitment prior to purchase. Item will come in original packaging. If you have questions, please contact the seller. Not responsible for improper or ill fitment due to incorrect year, make & model given by buyer upon purchase. fmf045648