This easy-to-replace combination filter (FR400) for the Austin Air HealthMate includes a HEPA filter a pre-filter and a carbon/zeolite mixture, The pre-filter is outside of the HEPA filter to protect the unit and extend the life of the main filter, These specialized filters offer unparalleled performance, Austin Air Purifiers are recommended for not only those with chemical sensitivities allergies and asthma but children and adults alike who want a better quality of living and breathing, Constructed of 60" sq, of true HEPA medical-grade material, These filters contain potassium iodide for absorbing formaldehyde ammonia and other VOCs, Filters 99, 97% of all particles down to 0, 3 Microns in size, Healthmate Filter, Black, SKU: ASTN025