The UTG Pro Mil-Spec 6-Position Buffer Tube is a CNC-machined receiver-extension tube for AR-15 builds running a mil-spec collapsible carbine stock. Flat Dark Earth finish. Stock not included. Fit: Mil-spec AR-15 lowers and mil-spec diameter collapsible carbine stocks. Will not fit commercial-spec stocks. Features: 6-position adjustable length-of-pull range CNC-machined from 6061-T6 aircraft-grade aluminum Precisely rolled threads for durable thread engagement with the lower receiver Tight tolerance control for a zero-gap fit against the receiver face FDE anodized finish - matches FDE Cerakote and FDE polymer furniture Best practice: torque to spec and stake the castle nut once installed. Pair with a mil-spec carbine receiver end plate, castle nut, recoil spring, and buffer if not already part of your build. Verify your lower is mil-spec before install.