1.We can produce a variety of tension spring according customers' sample. 2.Wire Dia:0.1mm-10mm. ... area.3) We have imported stainless steel,piano wire,carbon steel,phosphor,bronze and so on. Extension spring Industry's second most commonly ... their closed coil design and hooked ends. MaterialPiano wire, stainless steel, High Carbon Steel, Nickel Plated, Phosphor copper Bronze, Copper Bronze, Beryllium ...