The Penn-Plax Cascade Heat Aquarium Heater accurately maintains the desired temperature in your tank within 1 degree of accuracy. This heater can be manually set to any temperature however, comes preset to 76 degrees making them ready to use for most aquatic environments. Just plug it in and this aquarium heater will safely and efficiently bring the temperature of the water to your set level. Fully submersible, this heater can be placed horizontally or vertically in your fish tank and will automatically maintain the desired temperature level. Made with superior insulation, this aquarium heater provides excellent heat distribution over the entire element. The heavy duty shock-resistant glass gives this aquarium heater a long life and makes them safe for your aquatic pets. Aquarium heater comes with two suction cups for easy and secure placement in your tank. Heater measures 7 inches long by 1.5 inches wide by 3 inches deep and offers 25 watts of power. Safe to use for both freshwater and saltwater fish tanks.