Bushmaster Modular Carbine. Fluted 16" barrel, flip-up front and rear sights, izzy muzzle brake. Quad Rail vented free float hand guard. 1:9 twist Chrome lined. 500 rounds fired though it. Includes Bolt, Charging Handle, and Bolt Carrier. This upper has been well cared for and has no scratches and looks the same as the day I bought it. Cost new is $945, my price is $495 + shipping. Price without Bolt carrier group is $395. Pictures available if interested - email me.