The 45lb Box of Replacement Sauna Heater Rocks – LARGE holds peridotite stones averaging 4–6 inches, for large electric and wood-burning sauna heaters. Peridotite is a dense, coarse-grained igneous rock, and the bigger stone size suits heaters built to take larger rocks.
When you pour water over the heated stones, they give off soft, even heat for a traditional sauna feel. Use an igneous stone such as peridotite in your heater: rock that isn't made for sauna temperatures can crack under repeated heating.