Nu-Clo’s Dura Shock is extremely effective against algae, bacteria and other contaminants. Dura Shock is a premium blend of dichlor and additives that is 57% Sodium Dichlora-s-Triazinetrione with 35% available chlorine. It is extremely fast dissolving, 100% soluble, pH neutral and UV stabilized for longer life. Dura Shock can be used on all pools and surfaces. 1 lb. per 7500 Gallons. WILL NOT BLEACH VINYL LINERS!