Addax Tactical's AR Gas Piston Upper, the ATAC-GPU (Advanced Tactical AR Carbine Gas Piston Upper), utilizes a specially designed, self regulating, long stroke piston system, for enhanced dwell time and lower recoil. The ATAC has been designed to meet the demands of the rigorous use by military and law enforcement. The Addax ATAC's are built with the high quality military specifications and match grade AR15 components, which include military spec upper receivers, bolt carrier groups and barrels. Available options include Vltor MUR upper receivers, cold hammer forged 16 inch 5.56 barrels, a 10.5-inch long to 16-inch long barrel, compensator and flash hider options and special Cerrakote options.