Aluminium Coated Fiberglass
Each fibre is a very tiny sold glass rod.
Fiberglass has excellent heat resistance and in incombustible.
Fiberglass can not absorb water so it won't rot or decay and is resistant to acids, oils, many solvents, weather and corrosive vapours.
Fiberglass with an aluminium cover allows the material a 95% reflective heat property that makes it a very good material in high heat use.