An assortment of Hillman socket-head cap screws made from heat-treated steel alloy. Socket-head cap screws carry a recessed internal socket drive to add strength. They are commonly used on machine parts, manufacturing equipment, and other mechanical applications. Variants in this assortment range from #10-24 to 1/2"-13 in coarse screw thread size. Full assortments of #528 contain sixteen (16) refills comprised of Hillman item numbers #529 - #544.