The AR-STONER(TM) Upper & Lower Receiver AR-15 Action Block Set is a rock solid choice for building and maintaining your flat top AR-15. Constructed of heavy duty polymer, these solvent resistant blocks clamp in your bench vice to keep your rifle stable. Scratches, twisting and other damage is nearly eliminated with use of these blocks. Use the insert along with the block halves to avoid damaging your upper. With your upper receiver snugged down you have the right tool to remove, or apply correct torque to your rifles barrel nut. The AR-STONER(TM) lower receiver block fits into your AR-15's mag well from the top or bottom and is held secure by the magazine catch. With the lower secure you're able to clamp the block in your vice to build, clean or maintain your modern sporting rifle. Keep your AR-15 in place with the AR-STONER(TM) Upper & Lower Receiver Action Block Set.Note: Action Block Set fits majority of standard forged AR-15 upper receivers. Will NOT fit billet upper r...