IMI Defense Upper Vice Block Black. The Lower Receiver vice block completes the set and provides a safe solution that holds the rifle for assembly clean and repair. Features of IMI Defense Upper Vice Block The IMI Defense Heavy-duty blocks allow you to firmly clamp M16/AR15 receiver halves in a vise without risk of crushing twisting or otherwise distorting them when applying vise pressure or torquing the barrel nut. Keeps your rifle secure for safe effective cleaning assembly and repair. High pressure solvent resistant structural Rynite block and insert surround the entire upper receiver and support it inside and out to make re-barreling the M16/AR15 an easy one-man job. Lets you tightly clamp acarry handle receiveror flattop receiver in a large bench vise for barrel removal/installation. The torque generated while tightening the barrel nut is transmitted to the block and insert not the receiver. Minimizes the possibility of damage to the barrel detent pin and receiver detent notch. Holds securely without marring the finish. Package Contents: IMI Defense Upper Vice Block IMI Defense IMI-ZT002: Upper Vice Block Black