Harvia M3 SLM Series 16. 5kW Wood Sauna Stove w Exterior Feed The Harvia M3 SL stove is perfect for small and medium sized sauna rooms from 212 459 adjusted cubic feet (ACF). Required sauna stones 66 lbs (2 boxes) sold separately. If you are looking to get additional uses out of your sauna stove than this Harvia M3 SL is the stove for you. The M3 SL is placed in the sauna room and your firewood is loaded into the fire chamber from the other side of the wall. The