The Fluval A426 is the correct replacement cartridge for the following filters:
The Fluval A426 - G6 Chemical Filter Cartridge is compatible for use with Fluval G Advanced Filters. The Fluval G6 filter is a reusable cartridge that keeps the water in your aquarium fresh, clean, and clear. This Aquarium chemical filter features very efficient media that improves water quality.
Fluval A426 - G6 Chemical Filter Cartridge specifications: