Machine screws are used in conjunction with washers and hex nuts in order to fasten metal parts together securely. To ensure proper fit and quality of life, make sure to use machine screws with nuts of similar thread size and finish. Variants included in this assortment come in M5-0.80 & M6-1.00 coarse thread sizes and range from 10mm to 60mm in length. Full assortments of #45320 contain fifteen (15) refills comprised of Hillman item numbers #4388 - #4396 and #45321 - #45326.