Duda Solar thermowell030cm-SS 304 Stainless Steel Thermowell Probe for Temperature Sensors in Solar Water Heater Tanks & Pipe Length: 30cm/11.8 Material: 304 stainless steel Connection: 1/2NPT 304 stainless steel Hex Inner diameter of sensor hole: 7mm For use with &light;7mm od thermocouple sensors, see the Duda Solar Pt1000 & 10K sensors