The MR-3 Motor Terminal Release is a remote trigger for Nikon MD-3, MD-4, MD-11 and MD-12 motor drive. The MR-3 screws into the remote terminal on the motor drive. It converts 3-pin remote terminal on Nikon motor drives into a convenient auxiliary motor/shutter release button. Also serves for remote control when used in conjunction with the AR-3 Nikon cable release.
It permits the photographer to adopt a greater variety of shooting positions as well as provide an alternative shutter release button on the camera setup.