5 different apertures. 19 kinds of adjustable corrective lenses; lens range: -20D to +20D. Clip with integrated on/off switch for easy operation. Powered by 2xAA batteries (not included), allowing for simple battery installation and replacement. Compact design for convenient storage and portability. Precision construction with reliable performance. Classic instrument for medical professionals. Illumination: Direct illumination. Luminance: 14 lumen. Bulb: 106 2.5V, 0.5A; 206 3.0V, 0.08A. Operating conditions: Temperature: 10°C to 35°C Humidity: 30% to 70% Air pressure: 700 hPa to 1060 hPa Storage and transport conditions: Temperature: -20°C to 70°C Humidity: 10% to 90% (non-condensing) Air pressure: 500 hPa to 1060 hPa Color: As shown Material: ABS + Metal Package contents: 1 x Eye Checker Note: Light reflection and differences in display screens may cause slight variations in color between the product image and the actual item. Measurement may vary by +/- 1-3 cm.