Adapter, PTFE, 1/4in Thermocouple, 29/42 Inner Joint. PTFE adapter for use with either 1/8 or 1/4 thermocouples. Adapter has an outer Viton 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 Viton to provide a airtight seal between the adapter and thermocouple. Adapter design permits use with CG-145 Keck clips.