Thermocouples are best used for measuring temperatures that can go above 100 °C. This is a bare wires bead-probe which can measure air or surface temperatures.
Most inexpensive thermocouples have a vinyl covering which can melt at around 200 °C, this one uses a fiberglass braid so it can be used in high temperature measurements such as heaters and ovens.
K type thermocouple with glass over-braiding
Good up to 500 °C (900 °F)!
Color-coded wires
1 meter long (a little more than 3 feet)