Handy kit contains two Brownells tools that AR-fans all over the country have told us are indispensable for removing and installing barrels quickly. Our Upper Receiver Action Block wraps completely around any standard A2 carry handle or A3/A4/M4 flattop receiver so the whole thing can be securely clamped in a bench vise. An insert completely supports the inside of the receiver so there's no risk of crushing it or distorting it when your torque the barrel nut. Our Combination Wrench is an exact replica of the original military wrench for removing/installing the barrel nut. Has a cutout for a ½" torque wrench, plus ½", 5/8" and ¾" wrench openings for flash suppressors and other common accessories.