The 31-round .40 S&W magazine for Glock® from KCI is built to shrug off hard use and maintain reliable feeding, round after round. Constructed with a reinforced polymer outer sleeve and a stainless steel liner for extra support, just like factory mags, KCI’s magazine will fit both G22 and G23 pistols. KCI’s mag spring is made of tempered chrome silicon steel wire. Like many extended-capacity magazines, it needs to be loaded/unloaded several times with .40 S&W ammo before it will accept its full 31-round capacity. Try loading it to half capacity and leaving overnight to help set up the spring and make it easier to insert a full load later. Polymer body with stainless steel insert tube Baseplate is easy to remove for cleaning Witness holes for instance ammo status checks Accepts magazine accessories that fit factory mags Fits Gen3 & Gen4 Glock® 22 & 23 pistols The KCI 31-round magazine brings compatibility to the table, too: it will fit all Gen3 and Gen4 Glock 22 and 23 pistols with an ambidextrous mag release. And at these prices, you can afford to get a bunch. Double down on your .40 S&W Glock firepower today!