Diamondback Firearms OEM Replacement Barrel Grendel AR-15 6.5mm Grendel 18in Medium Profile Mid-Length 1-8 Twist 5/8 x 24 Thread 4150 CrMov Black. Made of 4150 CMV with a mid-length gas system. Specifications for Diamondback Firearms OEM Replacement Grendel AR-15 Mid-Length Medium Profile Barrel: Manufacturer: Diamondback Firearms Color: Black Nitride Finish: Nitride Caliber: 6.5mm Grendel Barrel Length: 18 in Barrel Profile: Medium Gas System Length: Mid Length Threads per Inch: 5/8x24 Barrel Twist Rate: 1-8 Barrel Material: 4150 CMV Steel Gun Make: Diamondback Gun Model: AR-15 Length: 18 in Package Contents: Diamondback Firearms OEM Replacement Grendel AR-15 Mid-Length Medium Profile Barrel What firearm models does the manufacturer say Diamondback Firearms OEM Replacement Grendel AR-15 Mid-Length Medium Profile Barrel is compatible with? The manufacturer says that Diamondback Firearms OEM Replacement Grendel AR-15 Mid-Length Medium Profile Barrel is compatible with AR-15Diamondback Firearms 65M18M50B8R: OEM Replacement Barrel Grendel AR-15 6.5mm Grendel 18in Medium Profile Mid-Length 1-8 Twist 5/8 x 24 Thread 4150 CrMov Black Nitride