eBay

Easily fix large masonry holes or cracks in your indoor or outdoor fireplace, stove, or other heating appliance
Build a solid fire pit floor or mold into custom firebrick shapes, the possibilities are endless
No heat cure required making your project much easier
25 pounds will cast a 12" x 12" x 3" block
For interior or exterior use, rated to 2,200 Degrees F (1,200 Degrees C)

Rated up to 2200 DegreeF (1200 DegreeC). used to cast custom shapes, to Replace worn-out firebrick or fill large holes in the Masonry firebox.