IIRC KAR is Ricoh's variation on the KA mount (Which is the full-program variation of K mount). It move the little pin which indicates a locked aperture ring to a different part of the mount (Coincidentally, but unfortunately, to exactly where the AF screw is on Pentax AF cameras, NEVER mount a Ricoh P lens on a Pentax AF camera, at least not if you ever want to swap lenses again).