These centering rings with a screen are used to filter the vacuum flow and keep objects from being sucked into your vacuum pump. They follow International Standards Organization (ISO) standards and have a flange size of LF-63, NW63. ISO flanged vacuum fittings are commonly used to build process vacuum plumbing and systems for industrial applications. The fittings are quick to assemble using double claw clamps and a centering ring (please see top right figure - click to enlarge). The Viton® centering ring contains a rubber/elastomeric o-ring. The ISO standard sizes for large flanges are LF-63, LF-80, LF-100, LF-160. These vacuum fittings are made of corrosive resistant 304 stainless steel and Stainless Steel 72 Mesh.