MEGABOMB HEADER: The science behind the MegaBomb header may be FMF's greatest engineering accomplishment to date. You can bolt on a Megabomb with an existing FMF Racing muffler for as much as a 3hp boost, plus the Megabomb actually reduces noises levels by as much as 1.5dB. The Megabomb technology is revolved to produce more low end to mid range gains as well as broadening out the mid to top end power gains over stock. Fits: Yamaha WR450F 2016-2018 YZ450F 2014-2017 YZ450FX 2016-2018