End flange O-ring for Hanovia medium-pressure ultraviolet disinfection systems, part 410032-0860. It seals the end flange against the treatment chamber and sits on the pressure boundary, so it is replaced whenever the chamber is opened rather than reused. Ordering by the 410032-0860 part number is the reliable route — O-rings of similar appearance across the range differ in section and material. Reference number 22149-1118.