... .3) We have imported stainless steel,piano wire,carbon steel,phosphor,bronze and so on. Extension spring Industry's second most commonly ... closed coil design and hooked ends. MaterialPiano wire, stainless steel, High Carbon Steel, Nickel Plated, Phosphor copper Bronze, Copper Bronze, ... ends are excepted.Free LengthThe overall length of a spring in the unloaded position.LoadOur computer can assist you ...