Erayco Digital LCD Fish Tank Aquarium Thermometer Digital Thermometer with external thermistor with 3 ft insulated wire. Easy to read LCD display Compact design, with suction cup and place to any smooth surface use Flip to switch between Centigrade and Fahrenheit On/Off button to save battery power. Temperature readings to within 0.1 degree, Submerge probe/thermistor into fish tank or a refrigerator or any place you want to monitor the temperature,simple operation Temperature range -50C ~ + 70C,Operating temperature -10C ~ +50C Submerge probe into fish tank to measure water temperature (Submerge probe only, do not submerge thermometer in water)