A Mineral insulated cable (MI cable) is a specialized type of cable used in high temperatures or harsh environmental conditions because it has low flammability, even when operating at high temperatures. It resists oxidation and enables precise measurement. MI cable consists of copper wires inside a copper, stainless steel, or Inconel® sheath, insulated by packed minerals such as magnesium oxide (MgO). Magnesium oxide makes an excellent electrical insulation material because it resists oxidation and ionizing radiation, and it is both chemically and physically stable at high temperatures. After the MI cable has been packed with MgO insulation, it may be rolled under pressure to achieve the desired diameter. The outer sheath protects the internal thermocouple wire from heat, chemical or other environmental damage. The metal sheath may be covered with an additional colored plastic sheath to add in identification and to add an additional layer of protection from corrosion.