1.3.5mm Spring 2.Material: 45#,60#,65#,C70DA,C82DA,70#,80#,72A,72B,82B. 3.Spring for mattres,shock absorbers 4.Best price 1. Product Name: 3.5mm Spring Of Grade 452. Material: Steel GradeGB StandardCarbon%Silicon%Manganese%Phosphorus%Sulphur %Chromium%Nickel%Cuprum%45#0.44-0.460.20-0.230.57-0.600.0090.0080.02-0.090.03-0.070.07-0.173. Production Standard: GB 3206-824. Main Markets: Argentina, ...