2a thread class right-hand 1.554" thread length flat countersunk head style 28 thread quantity per inch cadmium screw surface treated unf thread series
3a thread class right-hand 0.656" thread length flat countersunk head style 20 thread quantity per inch passivate screw surface treated unf thread series
3a thread class right-hand 0.422" thread length flat countersunk head style 28 thread quantity per inch retaining element in shank passivate surface treated unf thread series