Like all of TechT's bolts, the TM7 and TM15 MRT bolts have been through rigorous R&D and field testing. This testing guided the bolt to what is now the MRT. Initial prototypes saw the removal of the "cup seal" on the front of the stock bolt. After testing various other o-rings and seals, TechT decided that the MRT needed this cup seal on the front of the bolt for the best performance. The removal of this cup seal, like on other competitors' bolts, actually yielded worse efficiency and a loss of up to 15 fps compared to a bolt with the proper cup seal. This important recognition sets the MRT TM7 and TM15 bolts apart from their competition; no other aftermarket bolt maintains this important seal. The lightweight and clever design of the MRT Bolt make it the most efficient and fastest bolt available for your TM7 or TM15.