The Mk9 is our original 9mm platform. Designed to accept 9mm Colt-pattern SMG magazines, the Mk9 platform has evolved over time and now uses the same 9mm Radial Delayed Blowback upper receivers as our other 9mm platforms (MkGs, Mk17, Mk4). Mk9 Lowers are made from forged 7075 T6 aluminum and come with the Mk9 specific bolt catch, feed ramp, and magazine catch pre-installed.