For years, the name "Visi-Therm" has been the industry standard for excellence in aquarium heater performance and reliability. Now there is the Visi-Therm Deluxe - an advanced-design submersible aquarium heater that constitutes the next important step in aquarium heating technology. Water-calibrated to ensure precise temperature selection and superior performance, the Visi-Therm Deluxe delivers the ultimate in direct-set control, compact double-sealed durability...and certified accuracy to within one degree. With a simple "click" of the dial, you choose the ideal water temperature. The custom Double-Suction Mounting Bracket features an adjustable three-position window that ensures easy-to-view temperature setting. And, of course, every Visi-Therm Deluxe is CSA listed... designed to exacting standards for extended submersion and operational safety. 6 inches in length and is rated for tanks up to 20 gallons.