Dimension:

1.Material: high carbon spring steel, spring steel, stainless steel,SUS; alloy steel

2.Wire Diameter: 0.5-8.0mm

3. Surface treatment: become black,Zinc, Nickel, silver, golden, tin, powder coating,
   and shot blasting.

4.Certification: ISO9001:2000, ROHS

5.Can made by your drawings, sample and dimension

Formula:

1) OD=ID d (OD: outside diameter;ID=inside diameter; Dm=mean diameter; d=wirediameter)

2)F=Gd4*f/8Dm3Nact (F=load; G=gravity; f=deflection; Nact=active number ofcoil)

3)F''=F/f (F''=Spring rate)