Pins are used to hold together assemblies to fasten two or more common components to each other and serving as hinges, axles, aligners and pivots with stops that maintain a positive limit upon the movement of components within machinery and mechanical components. A piston is a component of reciprocating motors, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gastight by piston rings. In a pump, force is transferred for the purpose of compressing or ejecting a gas or fluid. Features. 06 x 17 SPE Steel Piston Pin. Made with high quality materialSpecifications. Size 06 x 17