American Tactical Imports MilSport AR-15 5.56x45mm NATO 7.5 inch M-LOK Upper Receiver Heavy Barrel 1-7 Twist 1/2x28 A2 Flash Hider Nitride Black. 56x45mm 7.50" Black Nitride Barrel - Specifications for American Tactical Imports MilSport AR-15 5.56x45mm NATO 7.5 inch M-LOK Upper Receiver: Manufacturer: American Tactical Imports Caliber: 5.56x45mm NATO Barrel Length: 7.5 in Barrel Profile: Heavy Barrel Twist Rate: 1-7 Firearms Threads Per Inch: 1/2x28 Muzzle Device: A2 Flash Hidder Finish: Nitride Color: Black Gun Model: AR-15 Handguard Length: 7 in Gun Rail: M-LOK Gun Type: Rifle Gun Make: AR Platform Barrel Material: Steel Magazine Included: No Additional Features: 1-7in. Twist Package Contents: American Tactical Imports MilSport AR-15 5.56x45mm NATO 7.5 inch M-LOK Upper Receiver What firearm models does the manufacturer say American Tactical Imports MilSport AR-15 5.56x45mm NATO 7.5 inch M-LOK Upper Receiver is compatible with? The manufacturer suggests that American Tactical Imports MilSport AR-15 5.56x45mm NATO 7.5 inch M-LOK Upper Receiver is compatible with AR-15American Tactical Imports ATI15MS556ML7: MilSport AR-15 5.56x45mm NATO 7.5 inch M-LOK Upper Receiver Heavy Barrel 1-7 Twist 1/2x28 A2 Flash Hider Nitride Black