Package includes 1 each Stainless Steel KF Swing Clamp with Stainless Steel/FKM (Viton) Centering Ring.Our KF NW Stainless Steel Swing Clamps follow ISO-KF standards. They are commonly integrated with vacuum systems with a vacuum level < 10E-8 mbar/Torr. 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. The centering ring contains a rubber elastomer o-ring. The standard sizes for quick flange fittings are KF10, KF16, KF25, KF40, and KF50 with flange sizes NW10, NW16, NW25, NW40, and NW50, respectively.