OASE Prefilterfoam Set 6 BioMaster 30ppi

The Pre-filter Foam Set 30 ppi for the BioMaster 250, 350, or 600 includes six coarse replacement filter foams.
The combination of coarse and fine filter foams allows you to customize to meet the filtration needs of your aquarium. It is best to replace the filter foams when you notice a decline in aquarium filter performance.