Sisu Sauna True to tradition, Finnleo saunas are made in Finnish style exclusively of fine grained Nordic White Spruce. Sisu rooms are light and well-ventilated, with a subtle hint of deep Finnish forests. The extensive use of Abachi white wood makes it comfortable to the touch - even at high temperatures. Abachi has no knots or splinters and resists stains as well as odor absorption. Pamper yourself with the soft, even heat from Finnleo's exclusive heater design. Direct contact between the elements and rocks eliminates the harsh metallic feel characteristic of lower-quality heaters