An assortment of class 10.9 metric flat-head socket 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 come in M3-0.50 and M4-0.70 coarse thread sizes. Full assortments of #43900 contain fifteen (15) refills comprised of Hillman item numbers #43901 - #43904 and #43906 - #43916.