Cast alnico is manufactured by pouring a molten metal alloy into a mold and then further processing it through various heat-treat cycles. The resulting magnet has a dark gray exterior appearance, and may have a rough surface. Machined surfaces have a shiny appearance similar to steel. It permits high temperature operation. Cast alnico 5 is the most commonly used in the industry: rotating machinery, motors, and instruments, sensor devices, holding applications and so on. Alnico 8 and alnico 9 has a higher coercive force and is usually used in disc shapes.