Real Avid AVAR15LLVB Lug-Lok Upper Vise Block Silver Aluminum Rifle AR-15The Lug Lok Upper Vise block uses the strength of barrel lugs to safely secure AR15 upper receivers while working, rendering clamp style blocks obsolete. The non marring, aircraft grade aluminum block slides through the upper receiver and into the star chamber of barrels. This takes the pressure from torquing away from weak, damage prone parts and puts it squarely on the steel lugs. Adjustable Vise Pins hold the block at the optimal working angle and