I'm so glad my sister in law pushed me to order a replacement kit as soon as I got my eufy 11S. Nothing needs replacing but I used 2 replacement filters alternating with the originals. Then when I take out my handheld vacuum, I clean them all and vacuum from the "dirty" side. I even vacuumed them up and then quickly sprayed them on the sink. Then I can dry them on the windowsill for a few days.