Nikon builds some of their cameras and motor drives with the tripod sockets way off centre, whoopsie! Fortunately, and by complete coincidence, they also make this handy device that can re-center tripod sockets. If you have a Nikon N2000, and N2020, or a camera with an MD-4/11/12/14 or 15 motor drive, the AH-3 will screw right in and put that tripod mount back where it belongs. In excellent condition, with instructions.