The Fortis Standard Castle Nut is made from a solid piece of billet aircraft grade aluminum that offers a significant weight reduction to your castle nut. If you're trying to save ounces, this is a great way, but without sacrificing durability. The castle nut will fit onto mil-spec buffer tubes and quickly upgrade the form and function of your build. Manufacturer part number: CN-Stand Fortis Manufacturing Castle Nut Specifications: Lightweight design at only 5.5 grams Castle nut made from 7075 T6 Aircraft Grade Aluminum Installs with a standard stock wrench Made in the USA