THIS IS A SINLGE PACK PRE FILTER This cartridge is pre-fill filter for pools, spas, aquariums or any use where using a garden hose water and you want it filtered and purified. Features: Hooks up to any garden hose Removes solids, grit, dirt, sediment, rust, calcium, iron and copper from your water. Helps prevent surface staining Reduces hard mineral deposits Easier to balance chemicals from the start Measures roughly 11" long x 3" in diameter FILLS UP TO 20,000 GALLONS!!!!