F.A.B. Defense GLR-16, Stock With Battery Storage Compartment, Fits AR Rifles, Black FX-GLR16B The GLR-16 Buttstock for your AR-15 provides you with enhanced versatility by being compatible with both Mil-Spec and Commercial diameter buffer tubes. It has a uniquely designed rubber butt pad for fast and stable shoulder positioning. There are three integrated slots for sling attachment: one in the front and two at the rear" plus two ambidextrous QD sling swivel sockets. A small water resistant battery storage compartment is included which holds (2) CR-123A or AA batteries.