LITTER BOX FILTERS: These cat little box filters are compatible with Cat Litter Box .Pre-cutting only needs to be installed directly..PACK OF 4: One pack contains 4 pieces of activated carbon filters, and one filter can be used for 2-3 months, but it also depend on the actual situations. Anyway, you can simply replace it when the filter loses the effectiveness..ABSORB ODORS: Activated carbon filters can effectively absorb odors, improve indoor air quality by absorbing the peculiar smell in the cat litter box..MATERIAL:These activated carbon filters (fibrous) are made of powdered activated carbon as the adsorption material, and the high-density polymer binding material is used to attach the carbon to the fiber. With the thickness of 0.5cm (0.2"), the filters can efficiently absorb odors..EASY TO INSTALL: Pre-cutting only needs to be installed directly. Due to its unique size, it is only compatible with Petmate Dome Cat Litter Box. You can also make it suitable for petmate basic cat box by cutting.