Chambered in 6mm ARC this RESOLUTE Upper Group is designed to pair with any standard AR15 pattern lower group. Harness the capability of 6mm in this uniquely designed RESOLUTE 16.1 upper. Available in six different Cerakote finishes all CMMG Upper Groups come complete with bolt carrier group and ZEROED accessories including: – ZEROED AR15 Polymer Dust Cover – ZEROED AR15 Ambi Charging Handle – ZEROED Muzzle Brake 6.5mm – Platform: Mk4 – Caliber: 6mm ARC – Operating System: Direct Impingement – Barrel Length: 16.1 – Barrel Twist: 1:7.5 – Barrel Contour: MT – Barrel Material: 416SS SBN – Barrel Twist: 1:7.5 – Muzzle Device: CMMG ZEROED Muzzle Brake – Muzzle Thread: 5/8 x 24 – Gas Port Location: Rifle – Gas Block: 0.750 Non-Adjustable – Upper Receiver: Billet 6061 T6 Aluminum – Hand Guard: CMMG EML15 M-LOK – Finish: Cerakote Standard – Charging Handle: CMMG ZEROED Ambi – Weight: 4.3 lbs – Length: 25