Tacfire AR15 Mil-Spec Buffer Tube/Aluminum Black. It has the tightest tolerance control for Zero-gap fitment with Polymer stock and receiver to meet most demanding silent operations. Compatible with Mil-Spec butt stock. Specifications for Tacfire AR15 Aluminum Buffer Tube: Manufacturer: TacFire Condition: New Package Contents: Tacfire AR15 Aluminum Buffer Tube Tacfire MAR040: AR15 Mil-Spec Buffer Tube/Aluminum Black