HuaxinYicheng Generic 18"x12" DIY Coarse/Course Foam Sheet Filter PAD Media Fish Tank (Pack of 3) Size: 18"x12" ;Thickness: 25mm(1") Grade of this foam:15ppi Course / Coarse Foam High quality,Performs mechanical filtration! Good for freshwater & marine environments Provides efficient water flow with less clogging for long lasting filtration