This is a Magpul Industries known as the BEV, model MAG536.
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 proper position. The BEV can also be turned over and used as a mag well vise block to support the lower receiver during maintenance" etc. Made in U.S.A.
Features:
Provides support for all AR15/M4 upper and lower receivers
Solidly engages barrel extension with steel lugs
Full-length steel support shank
