Increase the volume of your Glock pistols firepower by adding an extra magazine or two. Each factory magazine is built using a stiff metal tube encased in Glocks proven-effective polymer to resist magazine deformation and make them amazingly durable. Rounds are arranged in a double-row column with a viewing window for each cartridge so youll always know exactly how many cartridges are in the magazine. Per 3. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Handgun Magazines & Speed Loaders.