Material: Copper. High conductivity, corrosion resistant. Good electrical conductivity and thermal conductivity. It contains 300pcs / 9 sizes of the most commonly used copper washers. Ideal for sump plugs, water, fuel, and hydraulic fittings. Come with a plastic storage box for storage. Durable copper material that lasts for a long time. Perfect for electrical connections of household and commercial appliances, automobiles, and marine, in which the power source has a threaded / bolt connection. Engine Copper Washers Assortment Flat Washers Assortment Set Sealing Washer Kit Plain Washers for Hardware Accessories Product Features: Premium copper. Good electrical conductivity and thermal conductivity. Excellent for sump plugs, water, fuel, and hydraulic fittings. A drain plug washer to fit all types of engines: car, marine, generators, machinery and factories. Product Features: Product Name: Assorted Copper Washers. Material: Copper. Quantity: 300pcs. Package Includes: 300 x Copper Washer, 1 x Plastic Box.