Among refractory raw materials, due to the different phase composition and chemical composition, the same alumina content will show a huge performance difference, resulting in different application. M45, similar to the so-called Molochite, also called by mullite in China,only has two phases, mullite phase and glass phase, both of them have a small thermal expansion coefficient, so its thermal shock resistance is excellent, and it is often used in high thermal shock environments, such as kiln furniture.