Finish your carbine build with confidence using the Advanced Technology AR-15 Castle Nut. Machined from high-quality steel with a durable black finish, this mil-spec castle nut features a universal design guaranteed to work seamlessly with all standard buffer tubes. Engineered with four precision-cut notches to provide optimal purchase for your armorer's wrench, it ensures a rock-solid, secure lockup for your buffer assembly under the most demanding conditions.