Upper & Lower Receiver Vise Block Armorer Wrench for .223 5.56 Rifle Repair5. 56 223 A2 Upper and Lower Receiver Vise Block Set With Armorer's Wrench (Not a gun part!) This vise block set is the essential tool for general maintenance and repair of upper and lower receivers. All components are solidly manufactured with sturdy polymer material or powder coated steel. Upper Receiver Block Allows for safe clamping of upper receiver into a vise Fits both carry handles and flattop upper receiver Ideal for installing or cleaning