Leegoal Digital Aquarium Terrarium Fish Tank Thermometer(Black) 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 C and F On/Off button to save battery power. Simple operation Submerge probe/thermistor into fish tank or a refrigerator or any place you want to monitor the temperature.