Precisely milled mug that seems to do what it says. I don't have a lab for testing the water for pathogens, but I can confirm the water tates good. The UV light indicator comes on when I press the button in the cap. I have also seen in come on by itself, indicating the periodic sterilization cycle self-activates. The mug is attractive and fits in my carry-on pack's side pockets. It does not leak when the sip cover is secured. The carry handle should prove convenient. Note that the instructions specify only clean water be used. That surprises me a little, given that it exists to purify water. The mug is meant to function comparably to a Brita (or similar) pitcher, not to cleanse silty or muddy water, but to remove chlorine, lead, particulates, foul tastes, and other common annoyances and threats from municipal. The UV for killing organic pathogens is an extra level of protection, should you have to get water from clear source that has a higher than safe concentration. You'll want a Life Straw or other camping or survival purification solution for more extreme situations, such as purifying water from ponds, lakes, streams, puddles, and other untreated sources.