The GH Quartz Heater utilises high quality quartz glass for superior quality, and includes a thermal cut-off as well. The Quartz glass is designed to withstand rapid changes within temperature quickly, and is much more resiliant than standard glass.
The temperature of these can be adjusted between 20C and 34C, giving you complete control of the temperature of your aquarium, whilst the strong protective casing gives you peace of mind of complete safety.
The heater is fully submersible, and should be kept in the water at all times when turned on, as this actual cools the heater itself. It does contain a thermal cut-off, to prevent it from overheating, should the water level drop for example.