FMF Racing Yamaha YZ450F 03-05/WR450F 03-06 Q4 S/A Muffler - 044199

A 4-Stroke header system that incorporates FMF's patented Power Bomb module at a precise location in the initial stage of the header system; by positioning the "Bomb" at this key point, the expansion and contraction of exhaust sonics through the system resulting in a flow increase of nearly 10%. The surface of the perforated core lets the sound exit into the absorbing material (steel wool packing) and then allows the air to expand, cool and ramp back up at higher air pressures (RPMs). The Power Bomb is a "pre-muffler" of sorts, which helps to lower the bike's sound output because it provides more sound-absorbing surface area to allow the exhaust gases to become absorbed.