Guntec Castle Nut Features The Guntec USA Castle Nut is machined from steel and finished with a black nitride coating for corrosion resistance and a durable long-wearing surface. It is cut to mil-spec dimensions so it threads onto both mil-spec and commercial buffer tubes without needing a separate part number for each. Once staked against the end plate the nut keeps the buffer tube from backing out under the repeated recoil impulses of firing maintaining a tight stock assembly over time. This is the same style of component relied on in mil-spec AR-15 lower builds. Being made in the USA this castle nut gives builders confidence in its material quality and manufacturing tolerances compared to unmarked import parts. Its notched exterior is designed to work with a standard armorer s wrench for proper installation torque. Replacing a worn rounded-off or damaged castle nut with this one restores a solid connection between the buffer tube and receiver extension. Any AR-15 owner upgrading a stock repairing a loose buffer tube or completing a lower build from parts will need a reliable castle nut like this one. Guntec Castle Nut Specifications Manufacturer: GunTec Material: Steel Finish: Black Nitride Compatible Hosts: Mil-Spec/Commercial Buffer Tubes Country of Origin: Made in the USA Available At: GrabAGun