The Colt AR6721 Receiver Extention Nut is a purpose-built steel castle nut designed for AR-15 carbine and government carbine receiver extensions. Machined for a precise fit and finished in a subdued black, it helps secure the buffer tube to the lower receiver, supporting consistent alignment and dependable cycling over long-term use.

This receiver extension nut is ideal for AR-15 owners upgrading or maintaining their rifle, whether for regular range sessions, training, or general recreational shooting. Its straightforward design makes installation simple for experienced builders and careful hobbyists alike, while maintaining the clean, functional look many shooters prefer. Backed by Colt’s long-standing reputation for quality parts and careful manufacturing, it is a reliable choice for keeping your AR-15 running smoothly.

• Manufacturer: Colt
• Model: AR6721 Receiver Extention Nut
• Firearm Type: AR-15
• Color: Black
• Material: Steel