The Wilson Combat M4 Mil-Spec Plus, flat-top upper receivers are precision CNC machined from 7075-T6 aluminum forgings for maximum durability and Mil-Spec Type 3 hard coat anodized in rugged black. Whether you are building a match upper or a complete tactical rifle, quality starts with the upper receiver. This receiver comes unmarked for a clean, custom look. The same top quality upper used as the basis of our famous custom rifles. Due to the nature of forged uppers, some pitting and machine marks are natural and unavoidable. Please do not be alarmed by these marks, they do not effect function. 7075-T6 forgings machined to Mil-Spec Plus tolerances Mil-Spec type 3 Mfg: Wilson Combat