Mechanical Extension Springs are coiled products, in a variety of materials and forms. Extension springs are attached to two components from both ends of the spring, and when the components pull apart, the spring tries to pull the components together again. Extension Springs are wound to oppose extension.

Dependant on the application's load requirements, the springs initial tension can be manipulated. They are often tightly wound in the no-load position and have hooks, eyes, or spring anchors at the ends to attach to the components. Each spring is designed within proper stress levels and manufacturing limits.