LifeStraw water filter

I thought "is that really possible?"

Well, it is. Several health agencies tested and aproved its results. Indeed this is a really impressive item to have inside our backpacks when in some outdoor activity, especially in some unknown place to us.
I got mine a couple years ago and still use it, still trust it.
Here in Brazil this pretty a case of "big bucks", it costs around R$ 135,00 (around USD 55.00). I'm sure this can be found much more cheap in US or Europe.
Highly recommended.

I have a smaller straw type filter which I have used as backup, but I am hesitant to trust them on extended trips as a primary filter, even this one. For one, a hollow fiber (non-carbon) type filter will be destroyed if frozen. So you have to sleep with it- not a huge deal. Also, it is by design and definition impossible to dry this type of filter out completely (which is why you cannot freeze it- ice is "bigger"/less dense than water and so expands, rupturing the fibers so that they no longer function), meaning there can be leakage and small weight gain. It seems likely to me there is a molding danger during storage for long periods, but I am not qualified to say on that. This filter type also will be difficult to get water through. You will not enjoy sucking water through it for several days. Potential to block up is also high, and this type is appealing because you can drink from any source, however small or shallow, so you will be daring it to block up. The product recommends blowing through to backwash and keep the filter clean after each use. Promise is for 264 gallons, but remember that these tests are done using clean water with no microbes and the true to life result will be much lower, probably under 1/2 of that. (Think of sleeping bag temperature ratings- they are tested indoors, without wind, and off ground.)