NcSTAR Pro Series AR Barrel Lower Receiver Wrench Tan. You can remove/install M4 castle nuts with ease with this AR wrench. The castle nut wrench slips over the castle nut and nearly encompasses the castle nut for a more secure fit when installing or removing the M4 castle nut. Makes for assembling/installing collapsible stock buffer tubes a super easy task. The other end of the wrench is for installing/removing A2 Rifle buffer tubes (")". 1/2" and 3/8" drive compatible for torquing your barrel nuts to the proper torque specifications. All the tools are Clearly Labeled. Hole at the end is for hang Steel Construction Length: 12.5" Weight: 18 oz. US Patent Pending Specifications for NcSTAR Pro Series AR Barrel Lower Receiver Wrench: Manufacturer: NcSTAR Color: Tan Package Contents: NcSTAR Pro Series AR Barrel Lower Receiver Wrench NcSTAR VTARW4: Pro Series AR Barrel Lower Receiver Wrench Tan