Bests & Worsts Reviews from Amazon

This was the absolute BEST thing we purchased for our recent Everest Base Camp trek. It worked like a charm, and we used it multiple times per day. We never had to purchase bottled/boiled water. Another great thing (depending on where you are at) is that the SteriPEN doesn't change the taste of the water. That was great up in the Himalaya (Kathmandu was a different story). I really wanted to get the USB rechargeable SteriPEN. Although it would have been perfect for camping, it was going to be a pain on our trek. That's why we purchased this version. We went through 2 sets of batteries and we were on our 3rd. It functioned perfectly; we never had an issue. This also works VERY fast as opposed to iodine/chlorine tablets. Those can take up to 4 hours to kill cryptosporidia/giardia. The SteriPEN "kills" everything in 90 seconds. Granted, that's "per liter", but it's still a lot quicker. The only downside I can think of is "one liter at a time". It worked great for 2 people. I would certainly look for some kind of gravity device for large groups (not to mention you "only" get ~50 liters on new batteries). EDIT: 3/29/2016 I've had this pen for almost a year now (can't believe it's been that long since I was in Nepal). It's still holding up to a 5 star review. We've since taken on a couple of trips (one time to Mexico and one time to Guatemala). After reading some of the other reviews, I feel like I should mention that this works best with 1 liter, wide-mouth bottles. I actually purchased a Camelbak Chute (CamelBak Chute Water Bottle, Bluegrass, 1-Liter) to go along with this particular SteriPEN (and I needed a new water bottle anyway). You can treat less than 1 liter, but you should never treat more than 1 liter at a time (and no ice). For example, you could treat a glass of tap water (as long as it's deep enough to make contact with the contacts). The SteriPEN never reached the bottom of the Chute. However, there was enough room to agitate the contaminated water by sticking the pen down in and then swirling it around. All I can say is that neither my wife nor I ever got sick using this system.