... : 2.Material:Spring steel,stainless steel,zinc plating steel,etc. 3.Surface treatment:powder coating,nickle plating,chrome plating,zinc plating,etc4.Quality:ISO90001&ISO14001quality system ... in producing and selling all kinds of springs,like brake spring,waved spring,tension spring,wire formed spring,compression spring,torsion spring ect. industrial tension high quality hook spring