This is an apochromatic 120mm f5.6 enlarging lens, most commonly used to make photographic prints with 4×5 inch large format negatives. The 120mm focal length allows a much shorter enlarger column height (or larger prints) than possible with 150mm lenses often used for the 4×5 film format. It is equipped with user conveniences such as an illuminated aperture scale and aperture with click stop override. This model has 50mm x 0.75 mounting threads.