The FMF Power Bomb is a four stroke header pipe unit that has a unique bulge precisely located in the header system. A "pre muffler" of sorts, the Power Bomb actually lowers sound output because it creates more surface area to absorb the sound medium (exhaust). The surface area 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 with the higher pressure air. The result? The FMF Power Bomb is instrumental in reducing the decibel level on any four stroke and because of the expansion and contraction on exhaust through the system, the flow has been increased by nearly 10%. That means more power throughout the range.