... Outside diameter: 3.50mm Wire Diameter: 0.50mm Free Length: 17.50mm Detailed Information About the SpringMaterialCarbon ... , nickel, black, chrome plating, galvanizing, etc.Advantage High and durable quality, suitable price, fast deliveryApplication Housing appliance,automobiles, railways, ... and advised by customerCertification ISO9001:2008 Products dispaly high quality small double hook tension spring