Size 21 filter Fits PlasmaWave Series models: WAC5300, WAC5500, WAC6300, 5000, 5000b, 5300, 5500, 6300 & 9000. This is not a WINIX® OEM product and is not covered under any WINIX® manufacturer’s warranty. The WINIX® brand names and logos are the registered trademarks of their respective owners. This is a high quality replacement part.