Small World Replacement Cartridge 2-Pack give you two high quality replacement cartridges specifically designed to fit your Small World Filter bracket. These high quality disposable cartridges consist of carbon and zeolite for chemical filtration combined with a bio foam sponge. The zeolite crystals eliminate ammonia while the top quality activated carbon removes harmful gases and odors. The bio foam helps promote biological filtration leaving you with crystal clear water. Important for new filtration systems that may consume new cartridges sooner than normal while bringing water quality to healthy levels. This 2-pack insures you will have filters on hand when you need them and will help keep your small aquarium healthy and looking beautiful.