Decades of racing development went into the design of the FMF Powercore 4 complete exhaust to improve the power and performance of your dirt bike or ATV at a practical price. The FMF Powercore 4 is a muffler that will boost power and torque throughout the power range, making the Powercore 4 usable for all types of riding. FMF designed a Hi-Flo end cap and core for the Powercore 4 to increase power by creating a free flowing end cap and a core that allows room for exhaust pulse. This results in a consistent power curve. The FMF Powercore 4 uses and advanced cross-weave packing that is more durable then the traditional packing. The cross-weave packing also keeps the Powercore 4 at a reasonable sound level by dissipating the exhaust sound. FMF constructed the Powercore 4 muffler using aluminum to keep the weight down with a stainless steel head pipe and components for extended durability. Includes FMF Hi-Flo headpipe.