Rutland 62 Fireplace Dry Mix Patch Easily fix large holes or cracks in the masonry or mortar of your indoor or outdoor fireplace, stove, or other heating appliance No heat cure required, making your project much easier Dry mix formula makes enough to fill 15 cubic inches Sets as hard as firebrick when it is cured For interior or exterior use, rated to 2,200 F (1,200 C)