PTFE adapter for use with either 1/8" or 1/4" thermocouples. Adapter has an outer Perfluoro o-ring to form a grease-free, airtight seal between the adapter and the listed size of outer joint. The compression nut works in conjunction with the upper Perfluoro o-ring to provide a airtight seal between the adapter and thermocouple. Adapter design permits use with CG-145 Keck clips.