Made of durable nylon: Our material is nylon plastic. not rubber. Hard and inelastic. light weight. corrosion resistance. good insulation. environmentally friendly materials. common daily necessities: This box of assorted round washers contains 500 pieces / 8 popular sizes including the most common and common sizes -M2 M2.5 M3 M4 M5 M6 M8 M10 Practical plastic storage box: pre-classified for quick identification and protection against loss. Very convenient to use. General Intended Use: Increase the contact area of the bolt or nut with the workpiece surface to prevent wear of the workpiece surface. Versatile Gasket: Widely used in various fields such as semiconductor. automotive. aerospace and interior decoration. Mainly used in electrical connections. household and commercial appliances. car. marine. generators. machinery and installations.