Extended Magazine Releases for RugersModels to Fit Ruger Mk I† and II, Ruger Mk III, and Ruger *22/45 Pistols The Mk I/II† extensions make it much easier to eject magazines. The Mark III and 22/45 Extensions work very much like a 1911 magazine release. * The 22/45 fits both the Mk II 22/45 and Mk III 22/45 pistols. Mk I Pistols made before 1961 don't fit. These pistols have "A100" under the left grip panel.