The FMF Factory 4.1 slip-on exhaust is the same exhaust that professional racers use to bring home championships around the world. FMF constructed the Factory 4.1 slip-on exhaust to offer the lightest weight slip-on on the market. The technology in this slip-on exhaust cannot be found in any other exhaust. The proprietary Chamber Core technology allows for smoother and more efficient exhaust flow to maximize the power output. Since the Factory 4.1 slip-on exhaust is meant to be used for competition, FMF made this pipe ready to take to the track straight out of the box. The FMF Factory 4.1 has been designed to allow for easy maintenance with a removable sleeve for repacking and it offers the ability to fine tune the performance of the exhaust with the addition of tuning inserts and the option of a spark arrestor to give you no boundaries. The lightest system available. Boosts low-mid torque and offers a broader powerband with more over-rev. Patented Chamber Core for optimum performance. Engineered for compactness and centralized mass for improved handling. Exclusive mounting design. Easily serviced for re-packing. Slip-on mufflers are available with a titanium or stainless steel midpipe. Customizable with performance tuning inserts and spark arrestor module. Meets AMA sound requirements on most models. Detailed Specifications: Type: Slip-On. Construction: Stainless steel. Finish: Natural. Midpipe: Stainless steel. Note: For closed course competition use only. Not intended for street use.