This steel castle nut is an essential piece of an AR15 buffer tube/stock assembly. With standard cuts for use with armorers wrench, and smaller cuts for staking the castle nut and endplate for a secure hold, this part does everything it should at a good price. If youre in need of a spare for a new build or replacing a damaged component, this one is right for you. You can also add a little more color to your black rifle with with your choice of Cerakote finish. Specifications for AT3 Tactical Castle Nut for AR-15 Buffer Tubes: Manufacturer: AT3 Tactical Gun Model: AR-15 Fabric/Material: Steel Features of AT3 Tactical Castle Nut for AR-15 Buffer Tubes Finish: Black or colored Cerakote finishes Thread: Mil-Spec Compatible with armorers wrench Package Contents: AT3 Tactical Castle Nut for AR-15 Buffer Tubes