1. Unthreaded: the most cost-efficient solution. On the back of the thermometer a so-called front ring can be found, 15 mm in diameter and 10 mm in length. The front ring has a groove in it that may hold an O-ring or it may be fixed by inserting a bolt in the protective tube.
2. Threaded: a ½” male threaded connection can be found on the back of the thermometer for an easy fit e.g. into a cuff of identical size. The thread may be of galvanised steel, copper, etc. depending on its use.
3. The protective tube is a safe solution, as it avoids having to drain the entire system if the thermometer should fail or be damaged. It may be simply replaced as the protective tube closes the opening towards the system.