Visi-Therm is an advanced-compact design, double sealed submersible aquarium heater. Visi-Therms water calibrated thermostat is certified accurate to within one degree, ensuring precise temperature selection and superior performance. The Visi-Therm delivers the ultimate in direct-set control, with a simple "click" of the dial; you choose the ideal water temperature. The durable design is held to exacting standards for accuracy, extended submersion and operational safety. And the custom Double-Suction Mounting Bracket features an adjustable three-position window that ensures easy-to-view temperature setting. For up to 70 gallons salt or fresh water aquariums.