Used on machinery and equipment parts, the material is 5mm carbon steel spring steel wire, stereotypes after the wound into type, white zinc surface coated.
Technical Requirements:
1) Total number of coils: 7.5
2) Direction of rotation: right-handed
3) Diameter: 37.5
4) white zinc surface coated
http://www.weiyuanspring.com/various-types-of-tension-springs-torsion/05