Lightweight, long-lasting, inexpensive—all words that are music to a thru-hiker’s ears, and all of which describe the Mini. It weighs just 2 ounces and is a shorter than a beer can, but can filter up to 100,000 gallons of water. “With regular backflushing my Mini has performed impeccably for four years,” one tester says. The device screws onto most disposable plastic bottles, and you can use it on its own or with a reservoir hose. Its .1-micron hollow fiber filter protects against bacteria and protozoa, but not viruses. 2 oz.