NecksGen REVThe NecksGen REV is the more affordable option for those looking for a great head and neck restraint. Combining the safety of an SFI 38. 1 certified device, with the comfort of the small package of the REV, its just a matter of choosing which size works best for you. REV head and neck restraints come with a fixed length tether that will fit most drivers. Once you get your restraint you will need to do a slack test to ensure it is the right fit for you