Sustain® Summer Shield Chlorine Extender provides your pool with an extra level of protection against algae. It does this by creating a reserve, or back-up, of chlorine fighting power, that is released on-demand whenever routine sanitizing levels suddenly drop like after a rainstorm or pool party. Used according to label directions, one dose will last all summer (150 days).
Sustain Summer Shield
Chemicals are Non-Returnable