This is a k-type thermocouple wire with yellow teflon PFA fluoropolymer insulation, which is good up to about 260 C or 500 F. This k-type thermocouple wire can be used to make your own thermocouples for a wide range of applications, or to make your own extension wire. This wire has a small outer diameter, it is frequently used in research labs that develop rechargable batteries or battery packs for the automotive industry. It can alos be used for a wide rangge of scientific, manufacturing and engineering applications. The chromel alumel wire is made to standard thermocouple specifications. This is a solid wire, the type k metal conductors are AWG 30 or about 0.25 mm conductor thickness.