The key performance indicators for O-ring are reliability and variability. We fabricate these O-Ring, FKM for FV and HV systems. These centering rings are used for mating ISO flanges and include both the centering ring and O-ring. The ISO flange (also called Large ISO) is used for FV and HV chamber ports and is available in three distinct styles: ISO-KF, ISO-K which uses clamp fasteners and ISO-F which uses nut and bolt fasteners.