Factory 4.1 RCT Slip-On Exhaust. The Factory 4.1 RCT 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.