M2 Armament Group AR-15 Group 16in 5.56 NATO Upper Assembly Triangle Cut M-LOK Handguard Black. 56 NATO Complete Upper Receiver Group featuring Oct2 Series Partial-Pic Rail Handguard. Engineered for professional armorers competitive shooters and tactical riflemen this hard-use upper receiver assembly provides exceptional barrel stability while deleting unnecessary top rail bulk for faster target transitions. Specifications for M2 Armament Group AR-15 Group 16in 5.56 NATO Picatinny Upper Assembly: Manufacturer: M2 Armament Group Caliber: 5.56x45mm NATO Barrel Length: 16 in Barrel Profile: M4 Gas System Length: Carbine Length Barrel Twist Rate: 1-7 Firearms Threads Per Inch: 1/2x28 Handguard Type: Free-Float Muzzle Device: A2 Flash Hider Finish: Anodized Color: Black Gun Model: AR-15 Fabric/Material: 7075-T6 Aluminum Gas Block Journal Size-Diameter: .750 in Gun Rail: Picatinny Gun Type: Rifle Gun Make: AR Platform Barrel Material: 4150 Chrome Moly Vanadium Gas System Type: Direct Impingement Bolt Carrier Group Included: No Magazine Included: No Package Contents: M2 Armament Group AR-15 Group 16in 5.56 NATO Picatinny Upper Assembly What firearm models does the manufacturer say M2 Armament Group AR-15 Group 16in 5.56 NATO Picatinny Upper Assembly is compatible with? The manufacturer suggests that M2 Armament Group AR-15 Group 16in 5.56 NATO Picatinny Upper Assembly is compatible with AR-15M2 Armament Group M2-UPPER-C-OCTO-105: AR-15 Group 16in 5.56 NATO Upper Assembly Triangle Cut M-LOK Handguard Black