Compression spring in addition to participate in the deformation of the effective number of cycles n, in order to make the compression spring work force uniform, to ensure that the spring center line perpendicular to the end face, the spring at both ends of each 3/4 ~ 7/4 ring and tight supporting role, when the work does not participate in the deformation, so it is called dead ring or supporting ring.

The end of the extension spring has a hook for installation and loading. There are four types of common end structures. Semicircular hook ring and circular hook ring are easy to manufacture and widely used. However, due to the great bending stress in the hook transition, they are only suitable for spring whose diameter of spring wire is d≤10mm. Adjustable and rotatable hooks are under good stress and can be turned to any position for easy installation.