It is a dry-mix material,which when mixed with water, chemically sets as hard as a brick. Properly cast and dried, it withstands 2200°F temperatures.It can be used to fill large hole in the stove.or cast it into custom shapes tailored to the exact needs of the fireplace or furance.

Once set, it has very similar physical characteristics to fire brick. It has almost the same density, thermal conductivity and compressive strength as the fire brick,  it can be poured or trowelled into place, filling awkward gaps that would be very difficult to fill with bricks.