These KF-25 90 degree elbow vacuum fittings follow ISO-KF standards. They are commonly used for connecting vacuum plumbing and process systems. They are also called "NW" or quick flange fittings, "QF" 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. They are made of corrosion resistant grade 304 stainless steel.
KF-25 Elbow 90 Degrees
ISO-KF Flange Size: NW-25