The redesigned PowerBomb is a four-stroke header that incorporates FMF's patented PowerBomb module at a precise location in the initial stage of the header. By positioning this Bomb 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%! The outer chamber in the Powerbomb allows the air to expand, cool and ramp back up at a higher velocity. Additionally, the PowerBomb is a pre-muffler of sorts which helps to lower the bikes sound output by providing more sound absorbing surface area for the sound medium (exhaust gases). Made from premium American TiMetal material (Titanium). For Yamaha YZ 250 F (2001-2006) and WR 250 F (2001-2008).