Outstanding Material Our metal washers are made of high quality copper, which has good electrical conductivity, thermal conductivity, melting point 1083 and durable for daily use and can be used repeatedly. Easy to Use The O-rings are very easy to install, the surface of the copper flat washer is smooth, reduce friction between fasteners, prevent leakage, insulate, prevent loosening or pressure leakage. Easy to Store These copper flat washers are designed with a storage box, which makes the sealing ring gaskets safer and more convenient to store, easy to carry and maintain good classification. This design will improve work efficiency. Wide Application O-rings are great for water, sump plugs, fuel, and plumbing fittings. The hydraulic seal kit is perfect for electrical connections on household, appliance, automotive, and marine appliances. Ring washers are really nice tools. What you will get The flat washers include 30pcs M5*9*1, 30pcs M6*10*1, 20pcs M6*12*1, 20pcs M8*12*1, 20pcs M8*14*1, 20pcs M10*14*1, 20pcs M12*16*1, 20pcs M12*18*1.5, 20pcs M14*18*1, which is enough for daily use. "> Good quality product