Tacfire AR Lower Receiver Vise Block Black. It allows for safe mounting and will help to prevent any type of distort or damage to the Lower receiver. Great to use when performing your regular maintenance repairs or weapon assembly. Fits into the magazine housing from either the top or bottom and the magazine catch will securely lock your receiver into place in the vise. Specifications for Tacfire AR Lower Receiver Vise Block for .223/5.56 Mag Wells: Manufacturer: TacFire Gun Model: AR-15 Gun Type: Rifle Color: Black Length: 4.875 in Package Contents: Tacfire AR Lower Receiver Vise Block What firearm models does the manufacturer say Tacfire AR Lower Receiver Vise Block for .223/5.56 Mag Wells is compatible with? The manufacturer suggests that Tacfire AR Lower Receiver Vise Block for .223/5.56 Mag Wells is compatible with AR-15Tacfire TL008: AR Lower Receiver Vise Block Black