SPECIFICATION NJC-5 Lens meter Characteristies： INTERNAL READING Vertex Power Range:+20diopterto-20dioper Step:0.12D Prismatic Power Range:5 prism diopter Step:1 diopter Cylindnical Axis Range:0 to 180 degrees Step:1 degrees Lenses Accommodated Diameter: 20mm to 80mm Eyepiece Focusing:-5D to +5D Bulb:220V/110V-6V Direct current 3V