This 9mm Specific upper receiver, brought to you by our friends at H&R, is the backbone of your next Pistol Caliber build. This upper does NOT have a hole for a gas tube or the correct cam pin channel for DI BCG's. It is for 9mm, blowback operated, upper builds only.Harrington & Richardson uppers are manufactured from 7075-T6 and finished with Gray type 3 hard coat anodizing.