The dual-muffler configuration on the redesigned 2013 CRF450R gave Yoshimura the opportunity to create an entirely new muffler, specifically built for the CRF450R. Yoshimura worked in secret with Top AMA Pro Riders: Jeremy McGrath, Justin Barcia, Trey Canard, Eli Tomac, and Justin Brayton, to achieve maximum performance, mass centralization, and optimize rider-usability. Yoshimura were able to achieve all this, while keeping sound levels in check with AMA Regulation. AMA Pro and Amateur sound legal...out of box. Beginning with the head-pipe, a 3-stage tapered design results in better power, better throttle response, and usable power delivery. It is also spring mounted for increased durability. The header flows seamlessly into a re-configured tail-pipe, where the exhausts gases are separated to each muffler. Yoshimuras vertical divider splits the exhaust gases more evenly, for smoother flow, which improves mid-top power and throttle response. Divided exhausts gases then reach the new, dual RS-9 mufflers, hence RS-9D. RS-9s parallelogram-shaped muffler body increases muffler volume over the stock system, resulting in better throttle response and improved noise cancellation. The dual setup enabled Yoshimura to position the mufflers closer to the bikess center of gravity (mass centralization) resulting in better handling for the rider. An additional benefit of the mass centralization process was decreasing potential for muffler damage in the event of crash. RS-9D not only makes more power and torque possible, but does it more quietly than single systems. The uniquely sculpted carbon fiber end-caps feature a Tunable Insert System, able to fine-tune power delivery and decibel levels to rider specifications. Full System features dual RS-9 aluminum-sleeved mufflers with carbon fiber end-caps, stainless steel header and tail-pipe, installation hardware, and detail step-by-step instructions.