To utilize the Brownells AR-15/M16 barrel extension torque tool, insert the tool into the rear of the receiver until the teeth engage with the locking lugs in the barrel extension. Apply torque using a 1/2 inches torque drive through the tool to secure the barrel nut, employing a barrel nut wrench. This tool facilitates the application of straight-line torque for quick and efficient barrel nut installation while preventing damage to the exterior of the upper receiver. Compatible with any barrel nut wrench or free-float tube wrench and a torque wrench featuring a 1/2 inches square drive for precise application Engineered with precision from high-grade, heavy-duty steel bar stock to ensure extended durability and consistent performance over years of reliable service Compatible with AR-15, M16, M4 and BRN-4 style barrel extensions Barrel extension torque tool specifications of 9 inches (22.90 cm) length, 1 inches (2.50 cm) diameter