Flue Goo is a multi-purpose furnace/refractory cement. It will bond masonry to masonry, steel to steel, and steel to masonry. Flue Goo will withstand temperatures up to 3000 degrees F without cracking or shrinking. Flue Goo is freeze/thaw stable; however, it's still a good idea to bring it indoors in freezing weather. It comes premixed and ready to use, and is water soluble for easy cleanup. Comes in three colors: black, buff, and gray. It's packed in 1/2 gallon, 1 gallon, or 3 1/2 gallon plastic tubs. It is not for exterior use.