Compatibility: Replacement filter kit is compatible with Austin Air Healthmate FR400 Air Purifier filter. Fits Austin Air air purifier models HM400, HM402, HM405, HM410, HM450. Maintenance: Recommended to change this filter once every five (5) years under normal conditions, and more often under harsh air conditions. Package contains one (1) replacement filter and two (2) pre-filters. Approximate Measurements: 13.5 x 7.25 x 14.5 inches. Maintenance: Recommended to change this filter once every five (5) years under normal conditions, and more often under harsh air conditions. Package contains one (1) replacement filters and two (2) pre-filters. Approximate Measurements: 13.5 x 7.25 x 14.5 inches. Filter-Monster branded replacement filter compatible with Austin Air Healthmate FR400 Air Purifier filter. Package contains one (1) filter and two (2) carbon pre-filters. Engineered to fit Austin Air Healthmate (HM400) Air Purifier. Also fits Austin Air models HM402, HM405, HM410, HM450.