These O-Ring Nitrile/stainless steel carrier NW10 have part number C10511396, are new. NW fittings are the industry standard for vacuum components in the low and medium vacuum range and can be found on a variety of equipment. ISO fittings are joined by a centering ring and an elastomer o-ring. 

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 flange. 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 corrosive resistant Stainless Steel with Nitrile (Buna) O-Ring

KF-10 Centering Ring with Nitrile (Buna) O-Ring

ISO-KF Flange Size: NW-10