No battery required (operates on bimetal strip)Record the max-min temperatureAnti-rain structure design and can be hung in the outdoor use2 in 1 Thermometer Hygrometer2 Units: Celsius and Fahrenheit, Celsius / FahrenheitTemperature Measuring range: - 20 ~ 50 Celsius / 0-120FahrenheitHumidity Measuring range 0 ~ 100%Resolution Resolution: 1Celsius, 2%Accuracy of measurement Accuracy, plus or minus 2 Fahrenheit + / - 5%, (40% ~ 70%)Product Size Unite the Size: 128mm / 5inchesColour:GoldenMaterial:metalSize:Diameter: 128mmPackage Contents:1 x Humidity MeterOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.