Grabbing some mags for your Radial Delayed Blowback 9mm? These Gen II 9mm magazines work in Mk4/AR15 lower receivers with a CMMG 9mm Radial Delayed Blowback upper and feature the iconic CMMG styling with MORE capacity than the Gen 1 magazines, 33rd vs 30rds. Exterior dimensions closely match those of common 5.56 AR15 magazines for cross-compatibility with existing mag pouches and carriers.