These Leybold ISO-160 intake collar rings are designed to bolt-down an ISO-160K flanged fitting to the intake of a WA-2001, WAU-2001, WS-2001, or WSU-2001 model Root's blower vacuum pumps. The ISO-160K flange is typically used with double claw clamps. However, these bolt down collar rings include a snap ring that fits into a groove on the outside edge of the ISO-K flange allowing the bolt down collar to fasten the ISO-K fitting to the intake for the Root's blower vacuum pump. An extra sealing gasket ring (not a standard ISO-160 centering ring) is needed to form a vacuum connection between the Root's blower vacuum pump intake and the ISO-160K fitting (sealing gasket rings are sold separately on our Ideal Vacuum web site). These bolt-down intake collar rings are design for ISO-160K flanged fittings to be used with Leybold WA-2001, WAU-2001, WS-2001, and WSU-2001 Root's blower vacuum pumps and have Leybold part number 26751 (replaces older part number 361 16 126).