3b thread class right-hand 16 thread quantity per inch spline data, 40 teeth, 0. 930 in.face w, 10/20 diametral pitch, 30 deg pressure angle, 4.000 in. pitch dia, closed end w/center hexagon wrenching surface, 1.246 in. nom across flats by 0.820 in. lg wrenching surface terminated by 0.500 in. rounded extension, 1.280 in. lg with 0.532 in. nom dia hole drilled thru flat surface cadmium surface treated