Genuine Ruger factory magazines for your Ruger Mk I, II, and Mk II 22/45 Pistols. They're all specific to the model of pistol you have, so make sure to order the correct one. Mk III, MK IV, and other 22/45 mags are available elsewhere on this website.*Please Note, if ordering the MK I Magazine (015-90062): If your grip frame does not have "A-100" stamped on left side under the grip panel, the magazine follower button must be moved to the opposite side.