Winix replacement filter, upgrade for the Winix P450 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 25. Model 25WC. Item# 114290. Fits Winix models P450.