Replacing the paper filter elements is part of the daily maintenance of your swimming pool, and regular replacement of the cartridge will bring a high price. These washable and reusable foam filters can reduce your costs. The initial cost of this cartridge is slightly higher than the cartridge, but it is still longer than the cartridge This foam filter is longer lasting than your carton and can be washed and reused multiple times. It is recommended to change the cartons every week, and these foams can be simply cleaned and put back. You should be able to see the foam filter for 2 months. specification: Type: filter sponge Center drilling: about 40mm Colour: blue Material: sponge Size: 10.8 x 7.3 cm Package Contents: 8 x Filter Cartridge Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.