Tetra Whisper Bio-Bag Disposable Filter Cartridges make clear water simple. Ultra-activated carbon absorbs odors and discoloration better than competing brands, while dense, dual-sided mesh catches debris and fish waste. These economy cartridges are easy to assemble (includes carbon packets, thick'n fluffy filter bags, and aerobic frame with clip). For optimal performance, it is recommended that Bio-Bag Filter Cartridges be replaced once a month. Medium size cartridges fit Whisper Power Filters 10, 10i, E, J, and MicroFilter.