This Digital Thermometer features an easy to read digital display with temperature in either Fahrenheit or Celsius depending on your choice. The thermometer is accurate enough to create readings within 1 degree. Looking for a Thermometer for your Fish Tank? Our Digital Thermometer is a good choice for you Thermometer size: 2.17 x 1.46 in Cable length: 24.88 in Probe: Battery Each thermometer is equipped with a LR44 battery.the battery cover and insert battery with (+) positive side up. The LCD will now display the current room temperature. Operation: 1. Attach the display unit to the outside of the tank using the suction cups and submerge the probe into the water in the tank. 2. Press and hold the power (PWR) button to turn on. Hold the power button for 3 seconds to turn off. Package Contents: 2 x Battery 2 x Digital Thermometer 2 x Probe