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.Features :Reliable & durable next-generation impact & crush-resistant polymerBolt hold-open feature locks the bolt back after the last roundRatcheting Loading Lever takes tension off the spring for easy loadingDesigned to be left loaded for long term storageAnti-glare translucent window on rear of drumPaint pen dot matrix panel on back of body