Perfect Replacement Filter: This filter is ONLY compatible with Blue Pure 511i Max Air Puri-fier (F5max) NOT compatible with Blue Pure 511, 511 Auto, 211i max, 311i Max, 311i+ Max, 311 Auto, 411i Max, 411 Auto, 411i+ Max, Mini Max air puri-fier, 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 Premium materials: The Blue Pure 511i Max AllergenBlock replacement filter is made of high-quality non-woven fabric and activated carbon, using advanced energy-saving and low-density construction technology to provide fresh air True Filtration System: The filter effectively absorbs a remarkable 99.97% of particles as small as 0.3 microns, pet plush, household waste and dust Blue Pure 511i Max AllergenBlock Filter