Some of the most popular magazines used today are the Glock-pattern mags developed initially for the Glock G17 and compatible with some of the most popular 9mm Glock handguns on the market, including the G19 and the G26. These aftermarket Glock 17/19/26 polymer magazines bring enhanced capacity to these pistol platforms, as well as all of the other Glock magazine-compatible carbines and handguns available today. Each Glock 17/19/26 polymer magazine is built for use with the 9mm cartridge, and the magazine body is constructed using DuPont's proprietary Zytel polymer, which has been proven to be durable and long-lasting. Constant spring pressure is provided by a heat-treated Mfg: Pro Mag