These A&N CNC Quick Clamps are for KF-25 vacuum fittings and follow ISO-KF standards and have a flange size of NW-25. Used especially for high strength, corrosive, high torque, high heat and low temperature applications. Machined from solid bar for greatly increased strength. 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 circumferential clamp and centering ring form the vacuum seal between the connecting flanges (please see top right figure - click to enlarge). 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, respectively. They are made of SS 304 Stainless Steel.