HUUM DROP 6DROP Series 6. 0kW Sauna Heater The HUUM DROP 6 electric sauna heater is inspired by the purest element in nature a drop of water. This stylish compact 6kW wall mounted heater is engineered for sauna rooms up to 353 cubic feet (CF). Required control and sauna stones (4 boxes) sold separately. The design of the HUUM DROP sauna heater is inspired by the purest element in nature a drop of water. Its round design softens and livens up the angular interior