The RW Arms AR-15 Castle Nut (a.k.a receiver extension lock nut) is made the highest industry standard in the firearms market. This Mil-Spec castle nut is designed to be a replacement for worn parts or for a new custom AR15 build.
This AR15 Castle Nut is actually designed and manufactured to be staked. The castle nut design features a notched and circular configuration that screws on to the lower receiver extension. The nut retains the lower receiver extension because of it’s design. It also retains the lower receiver end plate in position. The standard mil-spec AR castle nut will have notches cut out of it, resembling a castle tower. The other side of the nut features smaller indentations that face the receiver and the endplate when the AR castle nut is installed. These smaller notches are designed for the staking process.