When they work... I tend not to invest in things that result in people coming to me for help when the item fails on the trail. There is a short list of items on my "do not waste money" list. The steri pen is on it. What would the hikers with failing battery operated devices do if I didn't always have a filter handy for them to borrow?

Of course, that is just my (frequent) experience.....
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"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzuki

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