Lennox Healthy Climate X8795 MERV 16 Maintenance Kit for PureAir Air Cleaner Model PCO20-28 Includes: (1) MERV 16 pleated filter model X8788 (1) PCO metal insert model X8791 (2) X8794 UV Bulbs For optimum performance, replace metal insert and lamps every 24 months. If you notice a significant drop in odor removal efficiency, replace insert more frequently. If you find that you need to replace the insert more frequently than every 24 months, consider source reduction and/or ventilation to reduce the levels of contaminants in your home. [Note: DO NOT WASH metal insert, as this will destroy the titanium dioxide catalyst that coats the insert surface.]