The redesigned PowerBomb is a four-stroke header that incorporates FMFâ€™s patented PowerBomb module at a precise location in the initial stage of the header. By positioning this â€œBombâ€ at a key point in the system, increased performance and flow is achieved through the expansion and contraction of exhaust sonics through the system. Result is a flow increase of nearly 10%! TheÂ outer chamberÂ in the PowerbombÂ allows the air to expand, cool and ramp back up at a higher velocity. Additionally, the PowerBomb is a â€œpre-mufflerâ€ of sorts which helps to lower the bikes sound output by providing more sound absorbing surface area for the sound medium (exhaust gases). On some models, you can choose between a moto or supercross version. The supercross version is designed for more low to mid-range power where the moto version is focused in the mid to upper RPM range.