An arm brace apparatus for use with a firearm allows for a reduced form factor when the arm brace is not needed by the shooter. The arm brace apparatus includes a hinge which allows for a substantial portion of the brace to pivot between an open or deployed configuration, a useful position when shooting, and a closed or stowed position, useful for transportation or storage of the firearm to which the arm brace is attached. A latch mechanism allows the device to be locked in either the open or closed position.