Used on 1351-01-531-3389. 3a thread class right-hand 0.580" thread length headless (setscrew) head style 20 thread quantity per inch setscrew, hex socket, cup point, alloy steel, cadmium plate, unf-3a alloy steel, cadmium plating per MS51964; hex socket end is reduced to 0.432/0.438 inch dia, 0.170 inch in lgt cadmium surface treated unf thread series