Adapter Nut (10050069): 3/8 A Bulb

The standard threading size at the end of a temperature gauge capillary tube is 5/8-18 UNF (Union Nut).

The inner threads of this 3/8 A Bulb Adapter Nut measure 5/8-18 UNF, to make the correct connection to the stationary end of the temperature gauge capillary tube. The outer threads measure 3/8-18 NPT allowing you to make a non-standard connection to match your application, which is generally a connection to the coolant bath of your engine block.