The 100317306 Centering Ring Assembly is designed for NW50 size ISO-KF vacuum flanges and features a silicone O-ring and 304 stainless steel construction. Centering rings are inserted between two same size ISO-KF flange faces to provide the vacuum seal when joining them. The included silicone O-ring is recommended for high temperatures up to 185 degree C. Series 31 ISO-KF vacuum components are designed for use at subatmospheric pressure and use standard interface dimensions defined by the International Standards Organization (ISO) allowing them to be interchangeable with other ISO-KF compliant components.