Genuine replacement cartridge to for oil water separator model WOSm2. The kit contains one pre-filter/activated carbon screw on cartridge. For proper preventative maintenance practices, replace these filter bags every 12 months/2000 hours of operation, whichever comes first or if the test sample exceeds 20 PPM oil content at the outlet. Oil content in waste water or trade waste is regulated by law. Oily water is not only an environmental hazard but can also be a slip hazard on workshop floors. An oil water separator should be used anywhere you have condensate being drained from a compressed air system.