A very important and highly specialized use of burned high-magnesia shapes is for small to medium-sized slide-gate plates for steel ladles with bore size less than 50 mm; the thermal expansion of magnesia is too high for large plates or bores, causing the latter to crack in service. In addition, burned highmagnesia, tundish slide-gate plates and porous upper nozzles are fabricated to control the flow of Mn- or Ca-treated liquid steel into continuous casting molds