Our quality fittings are the standard components for all vacuum and high vacuum applications. The high quality HENGKO components are designed and tested for leak rates less than 1 x 10E-9 mbar l/s. The choice of the best system depends on the required standards for example: cost-effectiveness, simple to fit and remove elements, leak tightness, high class materials or the demand for bakeable elements in the ultra high vacuum range. These centering rings with sintered metal filter provide maximum filtered protection for your vacuum system. They are useful in many situations in which a vacuum system or instrument needs to be protected from contamination by particulate generated from outside the system or from within. 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. These HKF-25 Centering Ring vacuum fittings follow ISO-HKF standards and have a flange size of HNW-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 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 HKF-10, HKF-16, HKF-25, HKF-40, and HKF-50 with flange sizes HNW-10, HNW-16, HNW-25, HNW-40, and HNW-50, respectively.