Enhanced Performance: IMPRESA Pure 411 Pre-Filter Replacements are compatible with Blueair Blue Pure 411 and crafted from durable nylon spandex. These washable filters prolong the life of your main air purifier filter by capturing dust and debris Effective Solution: Extend the longevity of your air purifier filter by using these replacement filters. Regular use helps prevent larger particles from reaching your main filter, maintaining your air purifier's efficiency Efficient Air Quality: These replacement filters are designed to capture everyday dust and pet lint effectively. Keep your home environment pristine with this 411 replacement filter, ensuring a cleaner atmosphere Convenient Washable Design: With a slip-on washable filter design, maintenance is a breeze. Simply machine wash and hang to dry, providing a continuous cycle of clean filters without additional hassle Consistent Freshness: The set includes four replacement filters, allowing for regular rotation to ensure continuous freshness. Always have a fresh 411 filter ready for use, supporting optimal air quality in your home