1/2" x 20 unf male fully threaded steel nut
SAE (45 degree/inverted/double) flare, .600” long overall.
American thread master cylinder brake line nut
For use with 3/16”/4.75mm OD (CNF-3)tubing with SAE flare.
Uses 1/2” wrench.
As the name implies, this is found most often at the master cylinder but is also found at ABS units and other places.