CMC Triggers Mil Spec Buffer Tube Kit, Black, 6 Position Tube, Spring, Buffer, Locking Ring & Nut, AR-15 81626 Compatible with Mil-Spec AR-15 stocks this kit contains all the necessary parts to mount a stock assembly onto your lower receiver. Six position AR-15 buffer tube is machined from 7075 T6 aluminum to Mil-Spec dimensions with a Type III Class II hard coat anodized finish. Buffer tube has through drainage holes to allow water to be evacuated in submerged environments. Machined high carbon steel Castle Nut and Quick Detach End Plate are heat treated for extra strength and given a nitride finish for durability and corrosion resistance. Kit contains a standard 3 oz. carbine buffer and a carbine action spring made of high-tensile steel.