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SteriPEN Adventurer Opti
$90, 3.6 ounces (including two batteries), www.steripen.com
The most inclusive purifier tested, the SteriPEN Adventurer Opti uses ultraviolet light to destroy bacteria, protozoa, and viruses present in untreated water, though it does not remove taste or odor. The SteriPEN is one of the fastest systems tested, bested only by the Hyperflow: it treats one liter of water in 90 seconds. Also small and lightweight, it doubles as a flashlight. At 1.5 inches wide, the SteriPEN will not fit into disposable water bottles. To remove silt or particulates, an additional filter is needed.