Description
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.
- Can be used with FMF or Stock OEM Header
See fitments for your model specific bike

![4.1 RCT S/S YZ250F 2019-22 w/carb end cap Slip On [A]](https://boydsassets.specd.nz/uploads/2026/07/a866b9d7-dd29-41fa-9dcd-2f33389c7e9f.jpg)




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