Winix WRF20CN Size 20 Sanitized Treated Replacement Carbon Pre-Filters use activated carbon to absorb chemical vapors and odors caused by cigarette smoke, pet odors, organic decay and cooking. SanitizedTM effectively reduces the development of bacteria, fungi and dust mites. Fit winix air cleaner models WAC5300, WAC5500, WAC6300, WAC5000, WAC 5000B. For use with Winix WRF20WH Washable HEPA Filters (sold separately). One year supply.