Size: 4.25*4.25*2.87 inch/10.8*10.8*7.2 cm Material: Sponge. The pool filter foam is the correct placement for the S1 type carton. Replacing a paper filter cartridge is part of routine pool maintenance. These clean, reusable foam filters will reduce your costs. reusable foam Replace S1 Replacing paper filter cartridges is part of routine pool maintenance. These clean, reusable foam filters will reduce your costs. Material: Sponge Size: 4.25 x 4.25 x 2.87 inch/10.8 x 10.8 x 7.2 cm (Approx.) Center hole bore: 1.57/4 cm (Approx.) Package Content: 4 * Filter Sponge