The Fluval U Foam Pad captures large particles and debris for effective mechanical filtration, the crucial first stage in the filtration process. It is custom-made to fit perfectly inside the filter chamber to prevent debris bypass. The Foam Pad has a pore size that allows efficient water flow, less clogging and long-lasting filtration. Genuine Fluval Internal U Series Filter Foam Pad Available for Mini, U1, U2, U3 and U4 Filters The Fluval Foam Pads captures large particles and debris for effective mechanical filtration, the crucial first stage. 3 X 2 PACK FLUVAL U2 FILTER FOAM CARTRIDGE FROM THE FLUVAL RANGE FILTER FOAM PAD CRUCIAL FIRST STAGE IN THE AQUARIUM FILTRATION PROCESS CAPTURES LARGE PARTICLES & DEBRIS FOR EFFECTIVE MECHANICAL FILTRATION WITH A PORE SIZE THAT ALLOWS EFFICIENT WATER FLOW, LESS CLOGGING & LONG-LASTING FILTRATION MADE TO FIT INTO THE U2 FILTER CHAMBER 3 X 2 PACK = 6 CARTRIDGES TOTAL RECOMMENDED THAT FILTER CARTRIDGES ARE CHANGED ONCE PER MONTH