The temperature is adjustable from 64°F and 94°F with an easy-to-adjust thermostat (see top view left). The heating function is indicated by an on/off control lamp. The glass jacket enlarges the heating surface and ensures optimum, even heat transfer. Thus, a smaller wattage than other brands will heat the same volume of water.
Constructed of shatterproof glass which makes them break resistant under normal circumstances. Models up to 150w are some of the smallest available.
The Science of Aquarium Heaters