ABC RIFLE COMPANY AR-15 Micro Pistol Build 5.56x45mm NATO 5in Barrel 4in M-LOK Handguard Upper Receiver Black. Its outfitted with a 5in 4150 CMV barrel chambered in 5.56 NATO boasting a rare 1:5 twist for optimal short-range stability. A .750 low-profile steel gas block and 5 3/16in stainless micro gas tube ensure smooth cycling. The 1/2x28 7075 aluminum flash can directs blast forward. A full-auto rated nitride BCG with 9310 MPI-tested bolt ensures durability. Includes mil-spec charging handle forward assist ejection port cover buffer system lower parts kit with A2 grip. Lower receiver not included. Specifications for ABC RIFLE COMPANY AR-15 Micro Pistol Build 5.56x45mm NATO 5in Barrel 4in M-LOK Handguard Upper Receiver: Manufacturer: ABC RIFLE COMPANY Caliber: 5.56x45mm NATO 5.56mm .223 Remington Barrel Length: 5 in Barrel Twist Rate: 1-5 Threads per Inch: 1/2x28 Muzzle Device: Muzzle Diverter Flash Can Fabric/Material: 6061 Aluminum Handguard Length: 4.5 in Gun Rail: M-LOK Gun Type: Rifle Gun Make: AR Platform Gun Model: AR-15 Barrel Material: Steel Bolt Carrier Group Included: MIL-SPEC Charging Handle Included: MIL-SPEC Package Contents: ABC RIFLE COMPANY AR-15 Micro Pistol Build 5.56x45mm NATO 5in Barrel 4in M-LOK Handguard Upper Receiver What firearm models does the manufacturer say ABC RIFLE COMPANY AR-15 Micro Pistol Build 5.56x45mm NATO 5in Barrel 4in M-LOK Handguard Upper Receiver is compatible with? The manufacturer says that ABC RIFLE COMPANY AR-15 Micro Pistol Build 5.56x45mm NATO 5in Barrel 4in M-LOK Handguard Upper Receiver is compatible with AR-15ABC RIFLE COMPANY ARPK15-ML4: AR-15 Micro Pistol Build 5.56x45mm NATO 5in Barrel 4in M-LOK Handguard Upper Receiver Black