Wheeler Delta Series AR-15 Upper Vise Block Clamp, 156-444: * Optimized for left- and right-handed Mil Spec A2 upper receivers with carry handles, as well as flattop-style receivers * Other AR-15 variants may be adapted with special attention to potentially non-conforming surfaces or features * Block allows you to safely clamp onto your AR-15 upper receiver in a vise, holding it securely without twisting, crushing or marring the finish * The perfect product for torquing a barrel on, removing a stubborn barrel nut or for simple gun maintenance and cleaning * Made of a high-pressure, solvent-resistant polymer material that can withstand almost anything you can throw at it * Includes a receiver insert with a gas tube alignment system, making sure your gas tube is always in line when installing a barrel and torquing a barrel nut