The ThermoFit makes it possible to retrofit the Oase FiltoSmart external filter with a Oase HeatUp heater.
FiltoSmart 100 uses the Thermofit 100 and suits the HeatUp 100
FiltoSmart 200 uses the Thermofit 200 and suits the HeatUp 200
FiltoSmart 300 uses the Thermofit 300 and suits the HeatUp 300
 
The heater is not included with either this Thermofit kit or the Filtosmart filter.