The Advanced Technology Int. AR-15 Pistol Buffer Tube Assembly fits most AR-15 and AR Variants. It is not compatible with AR-10 or .308 Rifles. It is constructed of Military Type III Anodized” 6061 T6 Aluminum and is virtually indestructible. The assembly package includes a Steel Military Grade E-Coated Castle Nut and Locking Ring along with a AR-15 Recoil Plug & Buffer Spring. It has a Mil-Spec Tube Diameter for Proper Fit to Specified Manufacturer’s Range for the Sig Brace” etc. Made in USA.