Ceramic fibre board - 12 mm thick - 200 mm x 200 mm. Rated to 1260 degrees. Ceramic fibre products require special care in use - ensure that you read and comply with all safety instructions. Manufacturer Safety Data Sheets can be found in the technical information section.
https://ceramaterials.com/wp-content/uploads/2019/09/CeramicFiberBoards-SDS-2300F-LD.pdf