F.A.B. Defense Tactical Buttstock with Adjustable Cheek Rest, Fits AR Rifles, Black FX-GLR16CP 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. This model includes an adjustable cheek rest.