Select your Liquatec empty water filter cartridge from the 4 sizes below. Liquatec empty water filter cartridges in "10, 20, 10" Big Blue, and "20" Big Blue sizes. The Liquatec EC Series empty water filter cartridges can be filled with any type of media. When the media is exhausted, new media can be exchanged for the exhausted media in the refillable cartridge. Email support@waterfilters.net if you cannot find your Liquatec empty water filter cartridge.