Hooded Litter Pan Filter, Helps Reduce & Absorb Unwanted Odors In Your Litter Box Area For Up To 3 Months, Doubles The Odor & Moisture Protection Combining Natural Charcoal & Zeolite, For Replacement Filters Use Zeolite/Charcoal Particles To Trap Airborne Odor Molecules, Absorbs Odors & Keeps Air Clean While Being Non Toxic & Easy To Load, Use With TV#'s: 506-635 & 683-302, Filter Designed To Fit Both Large & Jumbo Litter Pans.