I wouldn't rely on them. They are only effective to 3.0 microns. That's only partially effective against the larger bugs: Crypto and Giardia, and completely ineffective against bacteria such as Salmonella and E.Coli (which have a much shorter incubation period). Sawyer makes a 0.1 micron in-line filter that can be bought separately or as part of their water filtering bottle. I use one of these filters with a Camelbak Bite-Flip cap on a Nalgene 1L water bottle as my standard day hike filter. It can also be hooked up in-line in the hose of a hydration bladder, and is easily field maintainable.