This is a t-type thermocouple wire with blue PVC insulation, which is good up to about 105 °C or 221 °F. This t-type thermocouple wire can be used to make your own thermocouples for a wide range of applications, or to make your own extension wire. If this Type T wire is used to make an extension or to hook up a Type T thermocouple, it can correcty transmit the signal over the full measurement range, -270° to 370°C (-450° to 700°F). But the wire needs to be kept below about 211 °F so that the insulation does not melt. The copper constantan wire is made to standard t-type thermocouple specifications. This is a stranded wire with 7 filaments, it is more flexible than a solid wire and therefore especially useful for t-type extension wires. It is sold in 10 yard spools.