F.A.B. Defense GL-Core CP AR-15 Buttstock, Fits Mil-Spec And Commercial Tubes, Adjustable Cheek Rest, Black FX-GLCORECPB The GL-Core buttstock features an integrated cheek weld" ergonomic buttpad and an interchanging buffer tube adapter that allows it to fit on either Mil-Spec and Commercial buffer tubes. Comes with two integrated QD sling swivel sockets. The CP version includes an additional adjustable cheek rest" designed to support the use of different optics and holographic sights on the AK and VZ 58 platforms.