... here is what Bill's folks say:
The Geissele Premium Mil-Spec Buffer Tube is machined from quality 7075-T6 Aluminum and finished in Type 3 Hardcoat Anodize, available in Geissele’s DDC, at Charlies Custom Clones.
This rigid and durable buffer tube conforms to all Mil-Spec standards and features 6 stock positions. This carbine length and Mil-Spec diameter Premium Buffer Tube is made in the USA and weighs in at 3.7oz, making it the perfect fit for your AR-15 lower and ensuring compatibility with most Mil-Spec diameter quality AR15 stocks.
Included in the package is a high-quality, Mil-Spec castle nut and end plate.
