Vism Pro series HD M4 stock wrench for AR 15 castle nut. This Armorer's Wrench is a heavy duty steel M4 carbine castle nut wrench for collapsible stock A2 buffer tubes for AR type rifle. This AR15 castle nut spanner wrench cross section makes it easier on the hands to work on your lower receiver. You can remove and install M4 castle nuts with ease. 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. The other end of the wrench is for installing and removing A2 Rifle buffer tubes (¾")". 1/2" and 3/8" drive compatible, for torquing your barrel nuts to the proper torque specifications.