O-rings are a type of rubber sealing ring with a circular cross-section.
Because the cross-section is O-shaped, it is called an O-ring rubber sealing ring, also called an O-ring. It began to appear in the mid-19th century , it was used as a sealing element for steam engine cylinders.
Because they are cheap, simple to manufacture, reliable in function, and have simple installation requirements, O-rings are the most common mechanical design used for sealing.
O-rings withstand tens of megapascals (thousands of pounds) of pressure. O-rings can be used in static applications or in dynamic applications where there is relative motion between components, such as the shaft of a rotary pump and the piston of a hydraulic cylinder.