spring is an elastic object that stores mechanical energy. Springs are typically made of spring steel. There are many spring designs. In everyday usage, the term often refers to helical springs. When a conventional spring, without stiffness variability characteristics, is compressed or stretched from its rest position, it exerts an opposing force approximately proportional to its change in length. A tensioner is a device that applies a force to create or maintain tension. Force can be generated by a fixed displacement or by stretching or compressing a spring by changing the volume of a gas by hydraulic pressure or by gravity acting on a suspended mass. Features: Spring tensioner kit. Made of good quality material. Specifications: Length: 2.75 inches. Width: 10.95 inches. Height: 1.3 inches.