Y'all should really check out the Sawyer filter system.

http://sawyer.com/products/sawyer-mini-filter/

I've been buying these for $20 a piece. They are lightweight and take up as little space as the lifestraw, but look at how much water they will process, and their filter level is superior to the lifestraw.

For the money, this is a much better deal.

You can use it just like the lifestraw, or you can screw it onto the collapsible bag, or even onto a soda bottle.

These units are the bomb.

Watch their video Here:

http://sawyer.com/videos/sawyer-mini-water-filter/

This may be the best item I've ever recommended for survival.