Visi-Therm– Submersible Heaters from Marineland feature direct-set control, guaranteed durability, and certified accuracy to within one degree. Setting the temperature has never been easier, the easy “click”’ top dial now features calibrated marks, to confirm your setting from the top, that compliments the traditional side viewing sliding scale. They are the perfect choice for beginners and for longtime hobbyists alike who appreciate the ability to easily see and change temperature settings. The advanced mounting bracket provides three window positions to view the temperature display from multiple angles. No other aquarium heater is so easy to install, so easy to set, and so easy to use on a daily basis.  UL-approved for safe operation in both marine and freshwater aquariums.