A Hillman assortment of metric flat washers made from class 10 steel with variants sized M4 thru M20. Flat washers are great for adding resistance to your bolts and screws to prevent them from boring into the surface material and weakening it. When selecting a washer, be sure to pick one that matches the fasteners you are already using. The metric flat washers in this assortment feature a zinc coating for improved resistance to corrosion. Full assortments of #3623 contain ten (10) refills comprised of Hillman item numbers #3624 - #3633.