TheTamron-F AF Teleconverter 2X N-AFd MC7 for Nikon F is a 2x teleconverter that can double the focal length of a compatible lens, at the cost of two stops of light. Compatibility is pretty good: itll work with most lenses that dont have a protruding rear element. It even transmits pin-drive AF function, which no Nikon-branded teleconverter does. Inexcellent condition.