ATI Outdoors Buffer Tube Kit, Mil-Spec, Spring, Buffer, Locking Ring & Nut, Black A.5.10.2240 The Advanced Technology Int. Military-Spec Buffer Tube Assembly fits most AR-15 and AR Variants. It is not compatible with .308 Rifles. It is constructed of Military Type III Anodized" 6061 T6 Aluminum and is virtually indestructible. This package includes a Steel Military Grade E-Coated Castle Nut and Locking Ring along with a AR-15 Recoil Plug & Buffer Spring. Made in USA.