The fittings measure 5/16-18 inside and 9/16-18 UNF Outside.
A Hillman Brass Conversion Adapter (3/8" Female Tube x 5/16" Male Tube) Part #58359 is commonly used with brake line fittings
We make to order. There is a nationwide labor shortage. Please allow adequate time for us to build. Build times vary between 15 and 24 weeks at present.