... 304HC,304L,310S,316,316L,317L Surface:bright,polished,black Certificate:ISO,SGS Origin:China spring steel features:1 ... used for mattresses 3,spring steel Characteristic: 100% one wire splice free spring series, this kind of spring has ... the feature of one wire one time shaping chain structure, with even weight ... or caving in, but with integral type,heat high quality spring steel