【Compatible With】The 311i+ Max filter is compatible with Blueair Blue Pure 311i+ Max air purifier Compare to part #F3MAX+. Not compatible with Blue Pure 311i Max/ 311 Auto/ 311 (Non-Auto) air purifiers. Please check your machine model to avoid buying the wrong one. 【2-Stage Filtration High-efficiency】 311i+ Max replacement filter made of a high-efficiency filter，which helps you solve the problem of unpleasant odors，Pet odors，cooking smells, VOCs. This 311i+ Max air filter are capable of attaching 99.97% of airborne particles down 0.01 microns 【High quality materials】 Energy saving air filters save energy due to a low-density design and requiring less pressure to push air through the filter silent dual filtration technology provides cleaner air faster and more efficiently than using HE-PA filtration alone, resulting in less noise and energy consumption, making it more energy-efficient 【Usage Cycle】 Please replace regularly to keep your machine fresh，Recommended to change filter once every 6 months 【Customer After-Sales Service】 We are focus on providing High quality service, If you have any problem with 311i+ max replacement parts, please contact us and we will reply to you as soon as possible. The 311i+ Max filter is compatible with Blueair Blue Pure 311i+ Max air purifier Compare to part #F3MAX+. Not compatible with Blue Pure 311i Max/ 311 Auto/ 311 (Non-Auto) air purifiers. Please check your machine model to avoid buying the wrong one.