The 100315803 Adaptive Centering Ring Assembly is used to a join size NW25 ISO-KF flange to a size NW20 ISO-KF flange. Both of NW25 and obsolete NW20 size flanges have the same external dimensions and use the same flange clamps, allowing an adaptive centering ring to join the two flanges. This adaptive centering ring seal assembly is made with aluminum and features a Buna-N O-ring for the vacuum seal. Series 31 ISO-KF vacuum components are designed for use at sub atmospheric pressure and use standard interface dimensions defined by the International Standards Organization (ISO) allowing them to be interchangeable with other ISO-KF compliant components. Series 31 components can be used as modular building blocks to create vacuum piping systems. IS-KF flanges are "sexless" with a symmetrical seal so that so that components are rotatable. ISO-KF vacuum flanges are joined by inserting a centering ring between the two flange faces, and securing them with a flange encompassing clamp.