This item is an Eratac KeyMod Accessory, for use with KeyMod Systems. Specifically, it is a spare nut for KeyMod Accessories. Eratac continues their forward-thinking development of useful accessories for the competition and tactical marksman with the release of several Mil-Spec, high-grade aluminum KeyMod Accessories (compatible with KeyMod systems). Fully-machined from solid, high-grade aluminum All parts are Mil-spec, Type-III anodized (black), rendering them corrosion-proof No losable components Secure with Torx Screws and Nuts (also available) ERA-TAC ERATAC Key Mod Nut T0001-423A