9/16" x 18 unf male fully threaded steel nut, .600” long overall.
SAE flare (45 degree/inverted/double)
American thread master cylinder brake line nut
For use with 3/16”/4.75mm OD tubing with SAE flare.
Uses 9/16” wrench.
As the name implies, this is found most often at the master cylinder but is also found at ABS units and other places.