Spike's thermowell features a 1.5" TC on one end and a 1/2" NPT on the other. This allows it to attach directly to the TC fitting on a kettle. The NPT port on the outside allows for the thermometer to be screwed in. It also allows for an optional digital temp sensor to be attached.
The thermowell can be packed with thermal grease to help temperature response times.
-1.5" TC x 1/2" NPT