Suction Cups The 3 suction cups provided fit into the protective outer sleeve in a very unique way. They can hold heater vertical or horizontal under the water. Thermostatic Control This fish tank heater can automatically control the temperature. It will automatically turn off as the temperature rises above the internal setting you choose, and turns back on like clockwork once it sufficiently cools down. Specification: Diameter: Glass tube 1.02inch (2.6cm). Plastic housing 1.3inch (3.3cm). Cable length: 5-6.5 feet (150-200cm) Water Volume: 35-80 gallons Power: 300W Voltage: 110V 60HZ Adjustable temperature: 68°F~94°F (20°C~34.5°C). Outer Dimension: 15inch x 1.4inch x 1.4inch Package Include 1* Submersible Aquarium Heater 1*Heater protecter(with 3 suckers) Operation instruction: 1, The 300 watt aquarium heater could be installed horizontally and vertically, and it should be immersed into water completely.(It is recommended to be installed horizontally near the air pump.) 2, Heater reads E1: water shortage or wrong installation; please add more water or correct the installation. 3, It takes about 10~15 minutes to get used to the water temperature. Then adjust and set the desired temperature value. 4, Before powering, make sure the heater is completely submerged in the water. 5, Before removing the heater out from the water, make sure the heater is unplugged to avoid dry heating. 6, Please NOT put the aquarium heater into the sand as this will cause INACCURATE heating. Note: Due to unpredictable external factors, it's normal that the temperature difference is ±5°F. The temperature zone is 2 degrees each click.The small dot between each 2 numbers means 2 degrees difference.