The International Standards Organization (ISO) has defined the interface dimensions, allowing the interchanging of components that conform to the ISO-KF standard’s dimensions. The ISO-KF system is a modular, building block method of creating a vacuum piping system. There are several advantages in the use of ISO components. Since component dimensions are standardized, elbows, tees, crosses or valves for a given size may be interchanged. By using ISO components, system assembly is quick and cost effective. The Series 31 component line also includes a few components in NW 80 (3'') and NW 100 (4'') sizes. There is no international standard for these sizes in the KF style.