TacFire's AR15 Armorer's Kit is ideal for the home builder looking to build up a new rifle or service their existing weapon. The upper vise block is compatible with standard mil-spec 5.56 upper receivers and holds it in place. The lower vise block is compatible with either the top or bottom of the 5.56 magwell and locks into place with the mag catch. Its Armorer's wrench allows you to work on a 5.56 free-float handguard barrel nut, flash hider and castle nut. The wrench also features a tool to install an AR10/308 free-float handguard.