T-Series Nikkor lenses are view camera telephoto lenses which do not require a long bellows draw. This series of lenses may be increased or decreased in focal length, by replacing the original rear element with a longer or shorter focal length Rear Element.
This is a 600mm Rear Element Only. It will fit the Nikkor 800mm f/9 (1356) or 1200mm f/18 (1364) T series lens.