Make your own firebrick. Originally developed for use in blast furnaces,it has exceptional strength and abrasion resistance. It's ideal for casting into custom shapes to replace worn-out firebrick. When the dry material is mixed with water, it chemically sets and dries brick hard. It can be cast in irregular shapes or as a solid stone bed. 12.5 lbs. casts a block12"x12"x11/4", or 120 lbs./ cu. ft. Easy-to-follow fool proof directions on container.