They aren't completely different -- when the [included] dummy extender is attached to the back end of the rs card, it becomes the same size as an sd card, allowing it to be inserted and removed in a standard sd reader -- but only in its short form will it fit inside the 770 and allow the door to close. And while I suppose at least a micro sd is small enough to fit inside a half-length 'rs adapter', I don't know of anyone making such an adapter [but I'd be happy to learn otherwise].