Penn-Plax Cascade Heat Aquarium Heaters accurately maintain the desired temperature in your tank. Available in sizes to match the size and volume of your tank, these heaters are factory preset to 76 degrees Fahrenheit making them ready to use in most aquatic environments. Can be set to your desired temperature using the visible temperature setting scale and is accurate to 1 degree Fahrenheit. Just plug it in and these heaters will safely and efficiently bring the temperature to your set level. Fully submersible, these heaters can be placed horizontally or vertically in your tank and will automatically maintain the desired temperature level. Made with superior insulation, these heaters provide excellent heat distribution over the entire element. The heavy duty shock-resistant glass gives these heaters a long life and makes them safe for your aquarium and your pets. Each heater comes with two suction cups for easy and secure placement in your aquarium.