Compact and lightweight Nikon Auto Extension Ring PK-13 slides on or off your camera in seconds for a wide range of reproduction ratios. The PK-13 fits between the camera body and lens either single or in combinations, and retain automatic diaphragm and meter coupling with Nikkor lenses. This means you'are free to compose, focus and meter at the brightest, fullest aperture position without having to manually stop down the lens before shooting. These rings also allow automatic exposure control.