Wheeler's Delta Series AR-15 Upper Vise Block is optimized for left hand and right hand 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. Allows you to safely clamp on to your AR-15 upper receiver in a vise holding it securely without twisting, crushing or marring the finish For torqueing a barrel on, removing a stubborn barrel nut or for simple gun maintenance and cleaning Made of a high pressure, solvent resistant polymer material All-around product for your AR-15 gunsmithing, maintenance or cleaning needs Includes a receiver insert with a gas tube alignment system, making sure your gas tube is always in line when installing a barrel and torqueing a barrel nut Durable design holds receiver securely and fits both left and right-hand Mil Spec A2 upper, as well as flat top receivers