The CMMG® A1 AR-15 Receiver Extension and Stock Kit features a rear storage compartment and sling mount and includes everything you need for your rifle-length buffer system. The stock features high-strength polymer construction while the buffer tube features anodized aluminum construction. This kit includes A1 rifle-length buttstock, CMMG A1 buffer tube, AR-15 rifle buffer, and an AR-15 rifle action spring. Backed by CMMG's Lifetime Quality Guarantee.