The BT52 ACS/STR Picatinny Rail Adaptor for the popular Magpul ACS and STR style stocks provides the means to attach an Accu-Shot PRM style monopod (BT12-QK, BT13-QK and BT31-QK) to your Magpul ACS and STR Stock. The two piece adaptor replaces the polymer insert found on these stocks and is held in place with the supplied fasteners. Other than removing the buttpad and sliding the insert out, no modification is required. A 1/8 hex wrench is required but NOT included.