These rotatable bolt ring adapters are for making non bolted ISO-K collar flanges into ISO-F smooth bolt hole flanges. Standard ISO LF NW Centering Rings can be used. (see far right graphic above). The NW-80 ISO-KF 80 flange has 8 bolt holes. They follow International Standards Organization (ISO) standards and have a flange size of NW-80. 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 or bolts and a centering ring. The Viton® centering ring contains a rubber/elastomeric o-ring. The ISO standard sizes for large flanges are NW-63, NW-80, NW-100, NW-160, NW-200, NW-250, NW-320, NW-400, NW-500, NW-630. These vacuum flanges are made of non-corrosive aluminum.