Needle Tip Thermocouple, PTFE Coated, 3.5" Needle Length, Type K (YELLOW). Designed for use for small volumes, these 17 gauge hypodermic needle thermocouples can be inserted through septa into a reaction. They are PTFE coated and sealed at the end for liquid tight applications. Available in 3-1/2 or 7 inch lengths with 72 inches of PTFE coated extension wire.Please Note: Maximum Temperature for PTFE Coated Needle probes is 180¿C. They should only be inserted through rubber septa.