The 100312903 Wing Nut Flange Clamp is designed for NW25 size ISO-KF vacuum flanges. The wing-nut is hand tightened until metal to metal contact is felt. This aluminum flange clamp also works with size NW20 ISO-KF flanges which share the same flange dimensions as NW25 flanges.. 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. 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.