they are much lighter, easier to form, and insulate far better than dense bricks.refractory bricks etc refractory bricks etcItemMullite brickRe-sintered fusion mullite brickMullite corundum brickCorundum mullite brickHigh purity corundum brickMZ-70SDM-75MGZ-80GM-88GGZ-99Max. service temperature,oC16001650170017501800Al2O3, % ≥7075808899SiO2, % ≤25231880.2Fe2O3, % ≤0.50.50.50.30.15Bulk density,≥,g ...