1.Material:high carbon spring steel 2.Surface:blackem.nickel,zinc,chromed plated 3,SGS Certificate 4.OEM,ODM welcomed Blacken 2.5mm torsion wire forming spring parts for door lock(Samples welcomed):1.Material:steel,stainless steel.brass,aluminum,brass.cooper. carbon steel.2.Surface:zinc plating ,powdered,pas3.All our products are made by high-quality steels and first-class producing process4. ...