A few months back I wrote a review of Hydro Photo, Inc’s new SteriPEN Adventurer water purification system — innovative ultralight backpacking technology that uses ultraviolet light to give you a liter of virus and cryptosporium-free water with a single 2 1/2 – minute dose. My comments were based on my positive experience with earlier generations of the device and some kitchen testing. In the Granite Chief Wilderness north of Lake Tahoe June 13-16, it proved itself a worthy, trail tough companion. Over three days, three of us used it exclusively to purify about 35 liters. It worked flawlessly and the lithium batteries held up fine. It’s so light (3.5 ounces with batteries or 4.5 ounces with carrying case), I hardly noticed it on my belt during our day hikes of 8-10 miles. This is a must-have system.