Ideal for casting custom shapes to replace worn-out firebrick. It can be cast into irregular shapes, used to fill large holes or cracks in masonry fireboxes, or as a solid stone bed. A dry material that when mixed with water, it chemically sets and dries rock hard. Great for constructing outdoor fire pits and pizza ovens. Light brown when cured.From the ManufacturerIdeal for casting custom shapes to replace worn-out firebrick. It can be cast into irregular shapes, used to fill large holes or cracks in masonry fireboxes, or as a solid stone bed. A dry material that when mixed with water, it chemically sets and dries rock hard. Great for constructing outdoor fire pits and pizza ovens. Light brown when cured.