The TCO steel castle nut is a high-quality, Mil-Spec component designed for use with AR-15 carbine receiver extensions. Precision machined for a secure and reliable fit, this castle nut ensures optimal performance and durability in any build. Crafted from rugged steel and built to strict military specifications, it provides the strength and dependability needed for demanding applications. Proudly made in the USA, this essential component is a trusted choice for gunsmiths and firearm enthusiasts who demand the best for their AR-15 platform.