Aftermarket Particle Filters for 500/600 Series Air Purifiers, 3-Pack Replacement filter for 501, 503, 510, 550E, 555EB, 601, 603, and 650E air purifiers Traps 99.97% of harmful particles such as dust, pollen, and smoke down to 0.1 microns in size Anti-clogging gradient filter structure maximizes airflow and traps harmful particles Activated carbon technology combines with electrostatic and mechanical filtration for exceptional efficiency Prevents mold and bacteria growth using naturally antibacterial and 100% recyclable materials