The TS-3100-CI Series thermowells are made of 304 series stainless steel to ensure long lasting reliability and stability. These units are machined to high tolerances, so that there is no gap between the thermowells sheath and the probe, to provide maximum heat transfer. The TS-3100-CI Series thermowells are a 2-part thermowells. The sheath is set into the nut and then welded with an automated tig welder for consistency and from its own material to provide the strongest possible joint.