O-rings are rubber rings with an "O" cross-section. It is one of the most widely used in hydraulic and pneumatic transmission systems. It is mainly used to prevent the leakage of liquid and gaseous media in mechanical parts under static conditions. In some cases, O-rings can also be used as dynamic sealing elements for axial reciprocating motion and low-speed rotary motion. Its structure is simple, easy to install, low cost, easy to maintain, and various materials. It can be used as a seal for a variety of fluids such as oil, water, and gas. According to different conditions, different materials can be selected to adapt to it. 　　From the point of view of sealing principle, O-ring sealing ring is a kind of extrusion seal, the basic working principle of extrusion sealing is to rely on the elastic deformation of the seal, causing contact pressure on the sealing contact surface, the contact pressure is greater than the internal pressure of the sealed medium, then no leakage occurs, otherwise leakage occurs.