Pentax smc FA 31 / 1,8 AL Limited. Lens structure (elements/groups): 9/7, Fixed focal length: 31 mm, Minimum aperture: f/22. Diameter: 65 mm, Length: 68.5 mm, Filter size: 58 mm. Colour of product: Silver. Dimensions (WxDxH): 65 x 65 x 68.5 mm