The o-ring is mainly used for static gap sealing of fluids (such as water,oil, air chemical solvents, chemicals,etc.). The long-term using in the temperature between -60 and 220 degrees,it depends on the material, and the static pressure is less than 20Mpa. Sometimes used for dyamic, dynamic pressures less than 5 MPa, and also used for the semiconductor vacuum seals.

An O-ring is a circular seal that is commonly used in various mechanical applications to prevent the passage of fluids or gases. Made from elastomeric materials, O-rings can be found in a wide range of industries, including automotive, aerospace, and manufacturing.

The term "SI" in the context of O-rings might refer to "Silicone" or "System International," depending on the context. Here's a brief overview of both interpretations:

1. Silicone O-rings: Silicone is a popular material for O-rings due to its excellent temperature resistance and flexibility. Silicone O-rings can withstand a wide temperature range and are often used in applications involving food, pharmaceuticals, and medical devices.

2. SI (Système International): If referring to "SI" in a more general sense, it could involve the use of O-rings in applications that adhere to international standards or specifications. In engineering contexts, SI units (like meters, kilograms, etc.) might be used to describe dimensions and tolerances for O-rings.

If you have a specific application or context in mind for "SI O-ring," please provide more details so I can give you a more focused response!