This rifle is a transitional production SP6920MP-B rifle. I call it transitional because it has the early production ‘blue label’ but it has an ‘M4 Carbine’ rollmark lower that wasn’t integrated into production until later in 2011. The ‘MP-B’ in the rifles designation is simply an abbreviation for MagPul Black. This example sold on Gunbroker on 29 July 2019 for $849.00