[]: Premium Blue Pure 311 auto replacement fil-ters are compatible with for Blue Pure 311 auto air puri-fier. (20.5 inches machine). NOTE: Not fit for 311 non-auto, not fit for 411 models [2 LAYER FIL-TRATION]: 311 auto replacement fil-ters compatible with for 311 auto machine have 2-in-1 fil-tration systems. Particle Fil-ter attaching to up to 99.97% of airborne particles. Activated Carbon fil-ter take in pet odors and VOCs [SILENT TECHNOLOGY]: We deliver high-quality, and long-lasting replacements, allowing the fil-ter to last longer with a design. Compare to traditional HEPA fil-tration, we have a faster and quieter cleaning effect [EASY TO REPLACEMENT]: 311 true HEPA replacement fil-ter is easy to replace. It is tested for compatibility and service life and suggested to replace your 311 fil-ter regularly about every 6 months when used 24 hours a day to keep its performance<br><br>Color: As shown Material: Composite material<br><br>Package Contents: 1 * HEPA Replacement Filter<br><br>Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.