The unique design of the JW pet company smarttemp thermometer combines a thermometer with a magnet. The smart temp thermometer goes on the inside of the tank and the magnet goes on the outside to hold the smarttemp firmly in place, no suction cups needed. The smarttemp also offers a green safe zone which indicates the optimal temperature range. A high-end accuracy- (+/-) 1.5-degree f and the smartt emp has la rge easy to read numbers.