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 feature a coarse M4-0.70 screw thread and range from 8mm to 70mm in length. Full assortments of #43655 contain thirteen (13) refills comprised of Hillman item numbers #43656 - #43668.