Magpul Industries PMAG D-50, 9MM, 50 Rounds, Drum, Fits Double Stack 9MM Glocks, Black MAG1033-BLK Lightweight but incredibly strong" Magpul's PMAG D-50 GL9 is a highly reliable" 9x19mm Parabellum" 50-round drum magazine optimized for double-stack 9mm Glock handguns. Featuring their innovative bolt hold open" the D-50 reliably locks the bolt back on empty when used with firearms designed to lock back on Glock pattern magazine followers as well as a rounds remaining rear window" a high visibility follower and a capacity indication roller.