Winix standard replacement filter for the Winix PlasmaWave 9500 Ultimate Pet Air Purifier. One-year ultimate replacement filter set includes washable pre-filter, true HEPA filter, washable Advanced Odor Control Granular carbon filter and anti-microbial coating. Replace as indicated by filter change indicator (approx. every 12 months.) Pre-filter should be washed every 3 months; wash carbon filter as needed. Filter size 21. Model 21WC. Item# 114190. Fits Winix models: P300, 6300, 5300, 5000, 9500 and 9000.