Eheim Fine Filter Pads are designed to be used in the last stage of filtration to polish water of fine particles before it’s returned to the aquarium. They're made with a highly porous material that helps water evenly penetrate and holds coarse materials as well as the finest of dirt particles. This encourages good colonization conditions for beneficial bacterial cultures, which can help decompose harmful substances and keep your fish healthier. Please note the Eheim Fine Filter Pads should be replaced once they've become soiled to avoid damaging the motor head of the filter. However, they are designed to be reused several times. To clean the pads, simply rinse and then squeeze them out. Eheim offers these Fine Filter Pads for Eheim 2213 in an economical three pack. Fits eheim calssic 250 or 2213 filter.