LTWHOME Foam Sponge Filter Set Fit for Hozelock Bioforce 4500 Filter (Pack Of 3 Sets) Each set have 3 foams ( 1 x fine, 1 x Medium, 1 x Course) Foam Each Size : 198mm diameter and 50mm (2") thick Enhances biological filtration ,Good for freshwater & saltwater environments Custom Designed and Manufactured for Hozelock Bioforce 4500 Filter