【PERFECT FIT】 The 311i+ Max filter fully compatible with Blueair Blue Pure 311i+ Max, F3MAX+ 【NOTE】Not compatible with Blue Pure 311, 311 Auto, 311i Max, 211, 211+ Auto, 211i Max, 411, 411 Auto, 411i Max, 511, 511i Max, Mini Max, please check the model number before placing your order 【AllergenBlock Design】Effectively traps more than 90% of AllergenBlock particles. In addition to efficient performance, it can also save up to 10% of automatic delivery filters and extend machine life 【2-STAGE FILTRATION】Our 311i+ max filter is designed in 2-in-1 Filtration. With air filter and high-efficiency activated carbon filter for good clean filtration and performance 【SUPERIOR QUALITY】311i+ Max replacement filter is made of high-quality non-woven activated carbon and can adsorb 99.99% of air particles (with a diameter as small as 0.03 micrometers) 2 Pack Blue Pure 311i+ Max AllergenBlock Filter