HTH Granule Shock Treatment 12 lb. (Pack of 3)The convenient and easy to use product gives your pool a boost of chlorine for crystal clear water within 24 hours. The fast acting 4 in 1 shock product kills bacteria and algae, restores crystal clarity to pool water within 24 hours, reduces chlorine odor and eye irritation caused by improperly treated pool water, and wont fade liners. It is convenient, easy to use and wont over stabilize your pool. One bag treats up to 13,500 gallons of pool water.