These KF-20 KF-25 Quick Clamp follow ISO-KF standards and have a flange size of NW-20 NW-25. They are commonly used to build foreline vacuum plumbing and process systems. They are often called quick flange fittings because they are quick to assemble. A hinged polymer clamp and centering ring form the vacuum seal between the connecting flanges. The centering ring contains a rubber elastomer o-ring. The standard sizes for quick flange fittings are KF-10, KF-16, KF-25, KF-40, and KF-50 with flange sizes NW-10, NW-16, NW-25, NW-40, and NW-50. They are made of Polymer.