This 9kw sauna heater needs 20kg sauna stones(not included). 9KW - 13M³ (460 cubic feet). 9KW - 18-20kg(not included). Help to relax the muscle, relieve fatigue. Designed with an excellent steel structure for durability and corrosion-proof, the sauna heater can be used in a wet sauna room for a long tim e.