This is a flat washer that approximates the DIN 1440 or ISO 8738 standard. These polyamide washers distribute the pressure of a fastening head evenly over a surface. They ensure that the load or tension is maintained in the assemblies. They also prevent corrosion between the screw and the surface.
They can be used in combination with screws, bolts or studs. They are usually used for joint pins to connect dependent moving parts.