Lynn Manufacturing 1023 Ceramic 20" L X 3/4" H X 20" W Fiber Board, 2300F Rated | AF Supply
Amazon.com: Simond Store Ceramic Fiber Insulation Board - 2300F Rated - 0.47 Inch X 18 Inch X 24 Inch - Pack of 1 - Ceramic Thermal Insulation Board for Wood Stoves Fireplaces