Replacement Filter for 3M FiltreteT Ultra Clean Air Purifier - FAPF03. Fits Large Ultra Clean Air Purifier Model FAP03-RS. 2-Pack. Dimensions: 11-9/16" W X 21-3/16" H X 7/8" D To ensure that the air purifier continues to provide effective air cleaning, the filter should be changed after no more than 90 days of continuous use.