6801-06-04 Hydraulic Fitting 3/8" Male JIC x 1/4" Male O-Ring Boss 90° (Tube O.D. / Hose I.D. Size)
THREAD SIZES for 6801-06-04 Hydraulic Fitting: 9/16"-18 Male JIC x 7/16"-20 Male Boss 90°
To measure threads, Calipers work very well.