The Gasket Probe uses the same J-Type thermocouple as the Spring Probe. This probe replaces the gasket on 18mm spark plugs. The J-Type thermocouple has red and white color coded wires. Note that the spark plug plugs in some engines may run 50 to 100 Fahrenheit degrees hotter than the thermo well.

The gasket probe is recommended for use anytime the spring probe cannot be used. Aircraft fitted with thermo well TANIS preheaters should use the CHT Gasket probes.