This Zoo Med Digital Reptile Thermometer with External Probe is designed to accurately measure the temperature of your pet reptile's enclosure and help optimize its health. The digital thermometer features an external probe that allows for temperature measurement where your reptile sits, while the display can be easily viewed. The probe can be placed in wet or dry locations, and the temperature range is from -10 F to 140 F (-23 C to 60 C). Simply slide the Fahrenheit/Celsius switch to the desired setting. It operates using one LR44, 1.5v battery (included).