Cover directly onto the water inlet of your filter.Stop debris or very small / juvenile fish being sucked into the filter.Improve water quality with nitrifying ,Large particles will get trapped before entering the filter.Protect your filter, fish and shrimp by attaching this filter sponge over the water inlet.Easy to wash filter sponge can reduce the frequency of cleaning the filter. Keep your aquarium clean with this convenient filter sponge.Specification:Material: SpongeColor: BlackSize S(Dia.xH):Approx. 4.8x8.4cm / 1.89x3.31inchSize M(Dia.xH):Approx. 5.5x10.7cm / 2.17x4.21inchPackage Includes:4 piece Filter SpongeNote:Since the size above is measured by hand, the size of the actual item could be slightly different from the size above.Due to the lighting effects, monitor settings, etc. There could be some slight difference in the color of the pictures and the actual item