The BEV Block (Barrel Extension Vise) is an all-in-one compact vise block tool for AR15/M4 assembly operations of barrel nuts flash hiders etc. Mounts securely in a vise and provides support for both billet and forged upper receivers. Engages barrel extension with solid steel lugs and full-length support shank to prevent flexing. Steel hardness is optimized for durability yet won’t damage barrel extension and Magpul Polymer is used for all other engagement surfaces to protect aluminum receiver. O-ring post uses bolt carrier for additional stability and included Pin keeps upper in the proper position.