An assortment of flat-head socket cap screws from Hillman. Socket 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 #6-32 to 3/8"-16 in coarse thread size. Full assortments of #3889 contain sixteen (16) refills comprised of Hillman item numbers #3890 - #3905.