Universal Air Cleaner Carbon Replacement Pre-Filters Compatible with Honeywell 50250-S Round Air Purifier (1 Piece) Universal carbon replacement pre-filter designed for Honeywell 50250-S air purifier Helps trap larger particles like dust, lint, fibers, pet fur Easy to install it without cutting any more Effective air pre-filter removes common household odors, including smoke cooking odors and pet odors, keeps the air in your home clean and fresh Depending on where it is and how heavy the use is, the pre-filter needs changing every 2-3 months