Harvia Rounded Sauna Heater Stones Olivine Diabase (2-4 in, 33 lbs) are designed to give your sauna heater a natural, polished stone bed that looks as good as it performs. Sized between 2 and 4 inches, these rounded olivine diabase stones support steady heat storage and a smooth release of steam for both electric and wood-burning heaters. Their curved surfaces promote free airflow through the heater, helping the elements or fire work efficiently while creating a softer, enveloping heat sensation. A 33 lb carton provides a convenient quantity for refreshing the visible layer or completing a smaller unit. Resistant to cracking at high temperatures, these dense, genuine stones deliver long service life and consistent performance, while their river-rock appearance gives your heater a refined, spa-quality finish that Harvia sauna heater stones are known for.