You'll need this to screw a combo gauge temp probe into the head of your engine. Screw this into the head, then the temp probe screws into the inside threads. Useful if you switch temp sender from radiator to engine head, for more accurate engine temps!
This can also be used in the radiator if the temperature probe does not fit into the radiator all of the way. Be sure to use the sealing washer available in the drop down above if you use this for the radiator.
If you would like to get the sealing washer as well, be sure to add that in the drop down above.