Upgraded Litter Box Filter, More Carbon & Higher Ppi Filter Greatly Improves The Blocking And Absorbing Efficiency.eco-friendly Material, Made Of Activated Carbon, It Can Absorb And Filter Odors For Quite A Long Period, Disposable, Do Not Rinse. Package Includes,4 Pcs Carbon Activated Filter, Enough For Substitute, Average Is 2-3 Months Between Replacements. 17.5 X 6.3 X 0.2cm Useful To Litter Boxes: Easy Cat, Ginger, Zuma