The Advanced Technology International (ATI) Mil-Spec Buffer Tube Kit is a complete carbine receiver-extension assembly for AR-15 and AR-15 variant lowers. Machined from 6061-T6 aluminum and finished in military Type III hardcoat anodize, the extension is tough enough for high-round-count use without the wear or thread stripping you see on cheaper commercial-spec tubes.

Specs and features:

• Mil-spec diameter (1.148" OD) — pairs with any mil-spec collapsible stock
• 6061-T6 aluminum, Type III hardcoat anodized
• Includes steel E-coated castle nut, receiver end plate, and locking ring
• Includes AR-15 carbine buffer and action spring
• Made in USA

Compatibility: fits AR-15 and most AR-15-pattern (5.56 / .223 / .300 BLK / 9mm PCC) lower receivers. NOT compatible with .308 / AR-10 platforms — those require a large-frame buffer tube. Confirm your stock is mil-spec (not commercial-spec) before installing this tube; the two are not interchangeable.