Black, synthetic assembly features 2 waterproof storage compartments that hold 2 AA or 3 123 lithium batteries on each side. Buttstock features a hard rubber buttplate and 3 loops for sling attachment. Includes extension tube, recoil spring and buffer. Great adjustable stock to shoot with, the built-in cheek rest is a great upgrade over the standard M4 stocks. Commercial diameter buffer tube. Buffer Tube Outside Diameter: 1.178"