This is a factory replacement magazine for FNH rifles with the TBM bottom metal systems. These are built to the same specifications as the magazines shipped with FNH factory rifles. These magazines will also work with the TBM retro-fit trigger guard kit. These magazines are 308 Winchester caliber, and will not work with any of the WSM caliber rifles.
Rifles equipped with TBM trigger guards only. This magazine will not fit rifles such as the PBR that are provided with a factory 4-round flush fit magazine. You must install a TBM Trigger Guard (#932445) if the rifle does not already utilize the TBM detachable magazine system.