This AR-15 Upper Receiver Vise Block is a vital tool that enables you to securely clamp an A2 or A3 upper receiver into a bench vise without fear of crushing, twisting or damaging it in order to perform critical assembly, disassembly or maintenance tasks on your AR15 upper. Vise Blocks are ideal for use in torque AR barrel nuts to the proper spec, attaching or detaching a muzzle device. The Vise Block can even be useful for holding your rifle while cleaning your AR15/M16 and M4 rifle bore properly from the muzzle. The Vise Block is made from from durable, solvent resistant black polymer. The Vise clamp block is compatible with A2 Uppers A3 Flattop Upper Receivers. The Vise Block also has handy Quick Torque specifications guide on side.