A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, and pneumatic cylinders, among other similar mechanisms. It is the moving component contained by a cylinder and made gastight by piston rings. In a pump, force is transferred for the purpose of compressing or expelling a gas or fluid. A 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 features, is compressed or stretched from its rest position, it exerts an opposing force approximately proportional to its change in length. Specifications: Height: 0.1 in. Width: 1 in. Length: 0.95 in.