Okay, seriously considering the gravity systems, but as near as I can tell they're all Hollow Fiber which kinda freaks me out. The hollow fiber is basically just a bunch of tiny, fragile tubes. Dropping it or letting it freeze could destroy it's ability to actually clean the water, and you wouldn't know it until you were puking your guts out a week later.
I'd like to know just how likely it is to break these things. If you don't use it a lot, and don't go out when it drops below freezing, I guess it's not too much of a worry, but I feel like I'm too hard on my stuff...
Here is what the Sawyer website says about their Hollow Fiber Membrane. I don't think they are that fragile but if you are going to be in freezing temperatures you do have to take care to not let them freeze. I keep mine in a ziploc bag and keep it in an inside coat pocket during the day if it's below freezing and then keep it in my sleeping bag if at night. Not really a big deal.
Sawyer Filter Technology
With the technology derived from kidney dialysis, Sawyer worked with a fiber manufacturer to actually improve the hollow fiber membrane technology. In order to improve both the filtration rates and longevity of the filter, they needed something even more precise and rugged. The fiber composition had to deliver exactly 0.1 & 0.02 micron filtration 100% of the time to ensure no bacteria would get through, and the membranes had to be sturdy enough to withstand backwashing which allows the filter to be cleaning and reused.
Sawyer's Hollow Fiber Membrane filters are small, portable, easy-to-use, reliable, inexpensive, and can last more than a decade without needing to be replaced.
The proprietary water filters are comprised of tiny "U" shaped micro-tubes that allow water to enter into their core through tiny micro-pores. The high number of those tiny tubes and their surface area allows the filter to have one of the fastest flow rates in the world. This high flow rate eliminates the need to store water, reducing the possibility of water contamination after the filtration process.
Each filter is certified for ABSOLUTE microns; that means there is no pore size larger than 0.1 or 0.02 micron in size. This makes it
impossible for harmful bacteria, protozoa, or cysts like E. coli, Giradia, Vibrio cholerae and Salmonella typhi (which cause Cholera and Typhoid) to pass through the Sawyer PointONE™ biological filter. At 7 log (99.99999%) the filter attains the highest level of filtration available today.
If viruses are an issue, we offer the Point ZeroTWO Purifier (0.02 micron absolute pores), the first and thus far only portable purification device to physically remove viruses, which it does at a >5.5 log (99.9997%) rate, exceeding EPA and NSF recommendations.
All Sawyer filters have been tested by independent and qualified research laboratories according to U.S. EPA standards for water filters, and meet or exceed EPA standards. Sawyer's revolutionary technology has also been tested and verified by the United Nations, and is currently being used in more than 70 countries around the world.