All of our uppers and complete firearms are designated designated first with a Model (MK1, MK2, PCC) that designated the platform. MK1 is the AR-15 platform (.223 Wylde, .300BLK, 7.62x39), MK2 is the DPMS platform (.308, 6.5 Creedmoor), PCC is Pistol Caliber Carbine platform (9mm).
The number after the model designated the barrel length. For example a MK1116 is an AR-15 platform firearm/upper with a 16" barrel.
After the model and barrel length, listed is the specific design style (MOD 2-M, MOD 1-M, PRO). There are many differences between each line. To see the lines side by side/to compare, please click here.