... alternative 4.surface treatment: black painting 5. offer spring of good quality, on time delivery ... Xiaojinlong,etcMaterial availablecarbon steel wire, stainless steel wire, spring steel, brass, aluminum, copper, alloy, etcSurface ... treatmentpolishing, anodizing, zinc plating, nickel plating, etcTypeCompression spring,Auto spring,others.Applicationauto, toy, electronics, medical device, motorcycles, ...