5 different apertures. 19 kinds of adjustable corrective lenses; range of lenses: -20D to +20D. The clip features an integrated on/off switch for simple use. Powered by 2xAA batteries (not included), easy to install and replace. Compact size and design for easy storage and convenient transport. Elegant design and reliable quality. A classic instrument for physicians. Illumination: Direct Illumination Luminance: 14 Lumen Bulb: 106 2.5V, 0.5A; 206 3.0V, 0.08A Operation: Temperature 10-35°C, Humidity 30%-70%, Air Pressure 700hPa-1060hPa Storage & Transport: -20°C to 70°C, Humidity 10%-90% (without condensation), Air Pressure 500hPa-1060hPa Color: As shown Material: ABS + Metal Package Contents: 1 x Eye Checker Only the above package content is included; other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to vary slightly from the real thing. Measurement allowance is +/- 1-3 cm.