Includes: AR-15 Upper Receiver Vise Block or Lower Recevier Vise Block Material: Glass-filled polymer Length: 4.875" Weight: 4.6 oz Compatibility: AR-15 Color: Black Warranty: Lifetime This AR-15 upper receiver vise block conveniently conforms to your upper receiver allowing you to secure it on a table/workbench vise. Constructed of lightweight, heavy-duty glass-filled polymer, it's essential for the installation or replacement of barrel nuts, barrels, and muzzle devices, and forward assists on AR-15 rifles.