O-rings must be a strong contender for being the most useful and widely used component in industry. They are used in almost every engine, appliance, motor and hydraulic system. There are thousands of types of different O-rings, made from six principal materials and available in a wide range of sizes.
O-rings and rubber O-rings are employed where the pressure differential between the components of the system are static and / or the pressure differential between components is considerably less than that produced in hydraulic systems. The size of a rubber O-ring is delimited by the internal diameter (where the endpoints are the internal surface of the ring) and the cross-sectional area (where the endpoints are the external surface of the ring). In the UK, all O-rings and rubber O-rings are classified according to British standard sizes which extend from BS001 to BS932.