An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, reliable and have simple mounting requirements
