O-ring Gasket for older Dega Quiptron & early Onga Pantera cartridge filter.
Part 4 in Diagram.
Other Dega/Quiptron/Onga Cartridge Filter Parts
PS F-O5310860 / 5310860 / PS F-O5310850 / 5310850 / OPA_321-1339 / Dega 50, 75, 100, 150 / Onga PCF, BR6000 and BR9000