【Compatibility】: The filter is Only compatible with A*len BreatheSm*art Flex and 45i air purifier. Please check your model number before placing the order. 【High Effective Filtration】:3-Stage Ture HEPA clean up to 99.97% of particles as small as 0.3 microns. household dust, pet dander, and so on. 【Cost-effective Packages】: Includes 2 pack 3-Stage Ture HEPA filtration (Pre-Filter+Ture HEPA Filter+Activated Carbon Filter) also 4 pack extra replacement pre-filter 【Highly Recommended】: To your machine performance peak, you need to change the air filter once every 9-12 months, and Pre-filter every 3 months. 【We Treasure Our Customers】: Once you have any questions about our product, please feel free to contact us, and we will solve them for you within 24 hours. Filter made of FSC-Certified paper 45i Replacement Filter Compatible with A-len BreatheSm-art Flex Bh400 & 45i Pure Air Purifier, Compared # B4-Fresh/FL40-Silver-Carbon, 2 Pack 3-in-1 HEPA Filter + 4 Pcs Activated Carbon Pre Filter