An assortment of socket-head cap screws from Hillman. 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 feature a fine 5/16"-24 thread size. Full assortments of #43510 contain eleven (11) refills comprised of Hillman item numbers #2590 - #2592 and #43511 - #43518.