If fiddling with hoses and waiting for pills isn't your style, try the push-button AquaStar Plus. It uses UV-C light to zap protozoans, bacteria, and viruses. Fill the 1-liter wide-mouth bottle, screw on the cap/bulb, press the button to activate the UV light, and swirl until the green light tells you it's done (about 80 seconds). Our testers used this filter everywhere from the Adirondacks to Africa with no mechanical failures. Aquastar runs on CR-123A batteries, common in cameras, and the top will screw onto any wide-mouth Nalgene, though the bottle that comes with the unit has handy directions printed on its side. Bonus: The AquaStar doubles as an emergency lantern. Double-click the button and you get 15 minutes' worth of LED light before it auto-extinguishes. Warning: This unit is not for the clumsy. One drop on the right rock and the bulb could break. One more caveat: If your only water source is a mud pond, choose a filter like the Katadyn Hiker Pro. The death ray doesn't work in murky water. One set of batteries lasts for about 60 treatments.
Weight: 7.8 oz.