Feature: 1. Upgraded litter box filter, more carbon and higher filter, greatly improves the blocking and absorbing efficiency. 2. Universal, it well fits most hooded litter boxes. 3. Eco-friendly materials, made of activated carbon, it can absorb and filter odors for quite a long period, disposable, do not rinse. 4. Include, 4pcs/6pcs carbon activated filter, enough for substitute, average is 2-3 months between replacements. Note: This cats litter box filter uses high-molecular bonding material to attach good-quality powdered catalytic activated carbon to the foaming carrier. The activated carbon fiber filter cotton made by modern scientific technology has high carbon content and good adsorption. performance Material: Activated carbon fiber Quantity: 4 pieces, 6 pieces Size length x width: 15.5 x 16.5cm Thickness: 1cm Weight: About 16g/single piece Package List: Choice 1: 4pcs x Cats Litter Box Filter Choice 2: 6pcs x Cats Litter Box Filter