Because of the products unique formulation, minuscule particles of dust can be removed from the pool water, continues to work for up to 3 weeks. Removes algae spores. Reduces Chlorine consumption. Encapsulates the fine particles and holds them to the bed by means of a mild, glutinous formulation that is flushed away during backwash cycle. Dose one cube for pools up to 12,500 gallons. 4 BLOCKS PER PACK