High Temperature Noble Metal Thermocouple Assembly. Elements are provided to match the ITS 1990 curve. 24 ga. (0.020″) wire is standard – other gauges are available. Insulators & Protection Tubes w-Cemented Nipple are made of Alumina, Mullite, Recrystallized Silicon Carbide. Cast Iron or Aluminum Screw Cover heads are Standard. Porcelain Collar installed for Vertical Applications.