An automatic aquarium heater that utilizes an easy to adjust control dial with accurate one degree increments. Completely submersible for freshwater or marine use. Heavy-duty 2 mm thick shock resistant glass enclosures versus the common heater at 1 mm. Precision bi-stable thermostat with plus or minus 1/2 degree F holding temperature. Free of radio and TV interference. Six foot double insulated power cord makes this heater a durable one. No hot spots due to the chrome nickel helical coil designed for maximum life & even heat distribution. 150 W heater great for 40-60 gallon aquariums based on normal room temperature at 70 degrees.