Zapping water with ultraviolet rays kills all microorganisms, including viruses, making this a great choice for adventure travelers (viruses are generally not considered a threat in North American water sources). But it’s also so light and easy to use, some of our testers swear by the Opti for any wilderness trip with clear water (it doesn’t filter out particulates). During more than six months of testing, the Opti performed flawlessly, including in very cold alpine water.
Just push the button (once for a liter, twice for a half liter), dip the two-inch glass wand, and swirl for 90 seconds. At the end of the treatment, a green light indicates success (a red light means try again). “It’s idiot-proof,” says one tester. Two CR123 batteries treat up to 100 liters, and the company says the UV bulb lasts for 8,000 treatments. Caveats: The Opti only fits into wide-mouth openings, only treats up to one liter at a time, and is not the best choice for silty water. Eliminates: protozoa (including crypto), viruses, and bacteria. $100; 3.8 oz. (with batteries); steripen.com