HIVE Series 15.0kW Sauna Heater Package The HUUM HIVE 15STUX sauna heater package comes complete with the traditionally designed HIVE 15kW sauna heater, UKU control (Wi-Fi optional), UKU extension box, and sauna stones. This package provides unmatched efficiency and performance, and has been engineered for larger sauna rooms from 530 to 813 cubic feet (CF).