New and improved design is now fully submersible! Automatic aquarium heater is for both fresh and saltwater aquariums. Unit has a precision bi-stable thermostat with plus or minus 1/2 degree F holding temperature. Temperature is now easier to set with a new dial and accurate 1 in. increments from 65 to 93 degrees. Jagers have a 2mm thick thermal shock resistant glass vs. the common 1mm thickness for and extra sturdy construction. Heater also includes a 6 foot double insulated power cord; and a convenient clip-on heater holder.