The Ricoh AC-4c AC Adapter is compatible with the following digital camera models from Ricoh: GR Digital III, GR Digital II, GR Digital, G600, GX200, and Caplio GX100, R40, R30, R5, R4, and R3.
The AC-4c plugs into a wall socket. It's useful for providing power during long periods of shooting indoors from a relatively stationary position, or for powering the camera when transferring images to a computer while the battery charges.