This is what 2A Armament says :
This billet 6061-T651 Aluminum buffer tube is manufactured to same high 2A Armament standards and finished with hard anodize for lasting performance.
Billet machined Aluminum for tighter concentricity than a forging or impact extrusion to reduce potential for bolt carrier binding.
8 position adjustment with machined indicators visible through any stock with a viewing port located at the stock latch pin. Extended positions, increment adjustments have a finer spaced length of pull.
Mil Spec extension diameter of 1.148, and thread diameter of 1.185
Carbine length (8 inches)
Extended carrier support flange that supports the carrier for better anti-tilt performance.
Self aligns with the buffer detent.
Chamfered edges on the stock guide ramps for better feel
Weight 3.65 oz
Note: This item ships as the buffer tube only. A buffer tube assembly with latch plate and castle nut is also available.