Rounded Olivine Diabase sauna heater stones resemble nature's rounded stones from the great rapids, bringing a softer tone to your sauna along with multiple benefits. This stone introduces a soft steam method; the pouring water runs easily down to the lower stone layers. This way the water reaches more surface area, generating more steam with a softer touch. This method of using rounded stones on the top layer of the heater works in all sauna heaters. Please check heater description to see correct stone amount per heater.