JCW (Joint Castle nut Wrench) is a dedicated, heavy duty twin castle nut wrench, precision CNC machined from 4140 steel, heat treated and black oxided, it's something FDC has always wanted and needed. They couldn't find one they liked, so they answered their own prayers and made it. Like many AR users, FDC used either a heavy and unwieldy armorer's wrench, or a cheap stamped sheet metal castle nut wench that couldn't be used with a torque wrench, both work, but neither is great. One is overkill, the other is barely adequate. The handy JCW combines two castle nut wrenches in one. On one end, it has a conventional 3 lug castle nut wrench, spanning 18 Mfg: Forward Controls Design