We'll consider any item that can potentially save space or weight in our pack, and so we especially love items that do double-duty. Thus our initial attraction to (and subsequent love affair with) Vapur's MicroFilter, a super smart, flexible "anti-bottle" water bag that purifies potentially dangerous water on the fly, while functioning as a primary water bottle, too.

Available in two colors (olive green and night blue), the MicroFilter is a 2.7-ounce, 1-liter soft bag with a screw-in spout and a straw that works as an on-demand filter capable of removing 99.999 percent of waterborne bacteria, including marquee nasties like salmonella, cholera, and E. coli – as well as giardia, the one bug we worry most about when drinking from creeks. Add the BPA-free bottle's ability to collapse into a third of its size when not in use, and we're happy to toss out our bulky, hard plastic water bottle and never look back (except to recycle it, of course).

The technology behind the Vapur MicroFilter is not unlike the LifeStraw or other projects developed for those without regular access to clean water. The straw's filter is a hollow fiber membrane that has pores just .2 microns wide; these capture most bacteria, organic matter and protozoa (though, notably, it can't handle viruses or heavy metals). At the end of its 500-liter lifespan – which translates to just 14 cents per liter of filtered water – the pores automatically close to prevent potentially contaminated water from passing through, saving us from Montezuma's Revenge – or worse.

The one downside for us was that replacement filters aren't available for now, which means MicroFilter loses its superpowers and becomes merely a water bag, though Vapur says it plans to offer them in the near future. Nonetheless, we're still thrilled with the MicroFilter, and the ability to fill up on whatever water is at hand without fear – literally taking in a little bit of the land while we're exploring it. [$70; vapur.us]