EarthCare Replacement 93F Charcoal Filter Set for Norpro 93 Ceramic Compost Keeper & Stainless Steel Counter Compost Crock (1) Measures: 5.5" x 5.5" / 14cm x 14cm Charcoal filters help absorb odors that compost pails produce. Made as replacement filters for EarthCare and Norpros ceramic compost keepers, items #83, #93, #93R and #93EB. Filters should be changed approximately every 6 months, depending on use, heat and humidity. To replace filter, pull old filter out and toss. Inside replacement pack are two round filters. Only one filter is needed at a time and fits easily and snugly inside the lid.