High quality material : The lock washer is made of 65 manganese steel, with smooth surface, no burrs, black oxide layer, corrosion resistant. corrosion and Rust8 Sizes: This box of lock washers provides all the different sizes of washers you might need to use. Includes 7 sizes M3 M4 M5 M6 M8 M10 M12Convenient storage box: washers of different sizes can be well sorted in a transparent plastic box with separate compartments ;s for easy storage and easy pick up of required size Features: Star shaped lock washers can be used in bearings to apply spring force between the head of the fastener and the base material, which increases friction and resistance to rotationWide range of applications: it is a good choice for many occasions such as industry, gardens, homes, garages, workshops, car repairs, DIY projects , etc.