LTWHOME 18"x12" DIY Activated Carbon Impregnated Foam Filter Sheet(pack of 1) Size: 18"x12" ;Thickness: 12mm(1/2") The activated carbon in these sponges will absorb any impurities, chemically filtering your water High quality,Performs mechanical filtration! Good for freshwater & marine environments Provides efficient water flow with less clogging for long lasting filtration