HUUM CLIFF Mini 3.5kW Sauna HeaterThe compact HUUM CLIFF Mini 3. 5 kW sauna heater, with extremely short safety distances, is a wall mounted electric sauna heater that is especially engineered for smaller sauna rooms up to 212 cubic feet (CF). Because of its intelligent design, the CLIFF Mini has a much higher rock volume than other sauna heaters its size. A larger rock capacity results in a consistent, soft, high heat for a better sauna experience, greater efficiency, and more steam.