[Perfect Compatibility] - 2 pack replacement filters ONLY compatible with Blue Pure 511 Air Purifier. Please confirm your air purifier model and filter dimensions before purchasing. Filter Height: 8.27in (21cm), Width: 7.87in (20cm). Note: Not compatible with 311 Auto, 411, 411i Max, 211i Max, 311i Max, or 311i+Max. [High Efficiency Filtration] - Replacement filter for Blue Pure 511 air purifier features a dual-layer high-efficiency filtration system. The H13 True HEPA filter captures 99.97% of airborne particles as small as 0.3 microns, including pollen, dust, pet dander, and other allergens. The activated carbon filter helps reduce household odors from pets, cooking, smoke, wildfires, and VOCs, promoting a cleaner indoor environment. [Easy to Replace & Install] - Designed for easy installation and replacement without tools. It is recommended to replace the filter every 6 months, depending on air quality and usage. Compact design offers space-saving convenience and reliable performance. Color: White Material: Filter Paper Package Contents: 2 x 511 Replacement Filters Note: Light reflection and display differences may cause slight variations in color between the image and the actual item. Measurement may vary by +/- 1-3cm.