Harvia M3SL Woodburning Sauna StoveThe SL models are designed for people who want to conveniently heat their sauna from another room or outside the building. The opening direction of the door can be changed, making these stoves even easier to use. SL and Boiler stoves provide great bathing in small and medium sized saunas. Boiler stoves can be connected to a separate water tank. All Harvia stoves for through the wall heating and Boiler models are equipped with a glass door to give that