Clorox POOL & Spa Shock Xtrablue Pool Chemical, 1 lb Net Content, Bottle Container, Solid Form, Chlorine Odor/Scent, Blue/Green, Compositions: Sodium Dichloro-S-Triazinetrione, Boron Sodium Oxide, Pentahydrate, Aluminum Sulfate, Flammability: 0, 1.02 to 1.04 Density, 4.6 to 4.8 pHKills and prevents algae with algae-fighting crystalsKills bacteriaImproves filter performanceSwim-ready in 15 minFast-dissolvingContains algae-fighting crystals that kill and prevent algaeDestroys contaminants to aid filter performance and clear dull, cloudy waterFast dissolving formula works quickly so you can treat and swim in just 15 min