56mm(2.23") Aluminum Weld On American Style Coolant Filler Neck

This radiator and expansion tank filler neck is compatible with the most common style of caps available.  

Machined in the USA from 6061 Aluminum.

Vent port tapped for 1/8-27 NPT. 

Radiator caps for this style are available in a variety of pressures up to 40psi.