A single-purpose AR-15 armorer’s tool for torquing and staking the castle nut after a buffer-tube or end-plate install. The spanner head engages the castle-nut notches; the pin-slot tab seats the end plate flat against the rear of the lower receiver so it does not rotate as the nut is torqued down.

Specs & features:

• AR-15 castle-nut and receiver end-plate wrench
• Spanner head with pin slots for the castle nut
• End-plate tab for clean seating during torque
• Steel construction — handles the full 38–42 ft-lb spec torque
• 3/8" drive socket on the head for use with a torque wrench

This is a focused castle-nut-only tool. If you also need barrel-nut, A2 flash-hider, and stock-wrench functions, a full multi-function AR armorer’s wrench covers more of the build. After torquing the castle nut, stake it into the end-plate notch with a punch and hammer to keep it from backing off under recoil.