They are both mklll........third generations with mag disconects, a loaded chamber indicator. The standard Ruger pistol has had the mag release moved from the heel to the grip. The 22/45 is just a plastic version of the gun with a grip angle similar to a 45. The 22/45 has also had three changes to the gripp configuration also. The only operating differance between the two guns is that the bolt can not be released on the 22/45 by pulling it back. You must use the bolt release on this model. But for a first gun......get a .22