9 different common used sizes: M2, M2.5, M3, M4, M5, M6, M8, M10 and M12 Perfect for threaded/bolt-type connections on commercial and household appliances Easy to distinguish flat washers of different diameters Portable box makes it easy for you to carry Can be used several times in different occasions Nylon material makes it wear-resisting and high temperature resistant Serve as a bearing surface for fastener load distribution and resistance to abrasion