The teleconverter increases the focal length of your lens. It mounts between your lens and the camera body. A 2x teleconverter doubles the length of your lens. Thus a 200mm lens becomes a 400mm lens. We do have Kenko Pro, Kenko MC version mostly used for normaly lenses and small zoom lenses for bigger pro-zoom lenses we have Nikon TC, Canon TC version.
Kenko 2x MC7 MC-7 Teleplus DG Teleconverter Nikon - Mount Lenses The Kenko MC7 DG gives you the ability to extend the focal length of your lens by 2 times, it works with all range of lenses with Nikon Mount, in some cameras it may not compatible like Nikon D60, D40, D40x but with all other cameras it is full compatible
