What is an O-Ring?
An O-ring is a torus, or doughnut-shaped ring, generally molded from an elastomer, although O-rings are also made from PTFE and other thermoplastic materials. O-rings are used primarily for sealing.
O-rings are designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. The seal closes off a passageway and prevents an unwanted loss or transfer of fluid. It consists of two elements, the o-ring itself and a properly designed gland to contain the elastomeric material.
O-rings are one of the most common seals used in machine design because they are inexpensive and easy to make, reliable, and have simple mounting requirements. They can seal tens of MPA (thousands of psi) pressure.