Alexander Arms AR-15 6.5mm Grendel 16in Tactical Upper Receiver 1-8 Twist 5/8x24 Thread A2 Flash Hider Black Anodized. Specifications for Alexander Arms AR-15 6.5mm Grendel 16in Tactical Upper Receiver: Manufacturer: Alexander Arms Caliber: 6.5mm Grendel Overall Length: 23.5 in Barrel Length: 18 in Barrel Profile: Fluted Light Weight Gas System Length: Mid Length Barrel Twist Rate: 1-8 Threads per Inch: 5/8x24 Muzzle Device: Thread Protector Finish: Anodized Color: Black Gun Model: AR-15 Condition: New Fabric/Material: Steel Gas Block Journal Size-Diameter: .875 in Handguard Length: 15 in Gun Rail: Picatinny M-LOK Gun Type: Rifle Gun Make: AR Platform Barrel Material: 416R Stainless Steel Bolt Carrier Group Included: MIL-SPEC Charging Handle Included: MIL-SPEC Weight: 4.5 lb Magazine Included: Yes Mount Type: M-LOK Features of Alexander Arms AR-15 6.5mm Grendel 16in Tactical Upper Receiver Standard Charging Handle TCE Alexander Arms Branded Hand Guard One 10 Round Magazine Package Contents: Alexander Arms AR-15 6.5mm Grendel 16in Tactical Upper Receiver Thread Protector What firearm models does the manufacturer say Alexander Arms AR-15 6.5mm Grendel 16in Tactical Upper Receiver is compatible with? The manufacturer suggests that Alexander Arms AR-15 6.5mm Grendel 16in Tactical Upper Receiver is compatible with AR-15Alexander Arms UTA-65: AR-15 6.5mm Grendel 16in Tactical Upper Receiver 1-8 Twist 5/8x24 Thread A2 Flash Hider Black Anodized