Perfect Fit: 311i max replacement filter only compatible with Blueair Blue Pure 311i Max Air Pu-rifier F3MAX. Note: Not compatible with Blue Pure 311i+ Max or 311 Auto 2-Stage Filtration: Our 311i max filter is designed in 2-in-1 HEPA Filtration. With H13 HEPA air filter and high-efficiency activated carbon filter for good clean filtration and performance High Performance: The HEPA layer of blue air pu-rifier 311i max filter get rid of fine particles down to microns, and high efficiency activated carbon reduce various household odors. Creating fresh air for you and your family to breath and sleep easier Value Pack: 1 pack of blue pure F3MAX replacement filters included, and the filters are consistent and reliable. For best performance, it is recommended to replace the 311i max filter every 6-9 months, depending on your air quality and usage frequency Buy with Confidence: We deliver premium, durable and long-lasting materials, allowing the filter to last longer, they are efficient investments. If you have any questions about the 311i max air filter, we are always here to help you Compatibility: Nisreen’s 311i max replacement filter only compatible with Blueair Blue Pure 311i Max Air Pu-rifier F3MAX 2-Stage Filtration of 311i max air filter: Our 311i max air filter is designed in 2-in-1 HEPA Filtration. H13 HEPA layer and high efficiency activated carbon layer included Package Included: 1 pack of Blue Pure F3MAX replacement filters Regular Replacement: To optimize your Air Pu-rifier’s performance, it is recommended to replace your 311i max replacement filter EVERY 6-9 MONTHS, depending on your air condition and usage frequency