The Biocube premium filter cartridges feature dual-action filtration. The dense woven floss acts as a prefilter to clear detritus and debris while the activated carbon removes odor, organics and discoloration. The rigid frame ensures that water passes through the cartridge and not around it for optimal water filtration. This filter cartridge is designed to fit all BioCube all-inclusive aquarium systems, which include sizes 8, 14, 29 and HQI.