The Tetra Easy Crystal Filter Box containers provide crystal clear and hygienic water. Quick replacement of cartridges without getting your hands wet. Intensive mechanical, chemical, and biological filtration ensures crystal clarity and healthy water parameters: - Mechanical and biological filtration: the double-layer filter cartridges capture even the smallest impurities. - The white part is responsible for the preliminary cleaning of the water before filtration. - The beige part is responsible for proper filtration. - Cartridge replacement without having to rinse the filter - without getting your hands wet. - The Timestip indicator shows when the filter element needs to be replaced. Packaging format: Filter inserts.