"Oh man, you just turned our campsite into an ER!" The CleanStream is a gravity filtration system that resembles an IV bag. Consisting of two Platypus bladders, two hoses, and one 0.2-micron-thick hollow fiber filter (w/a cartridge that's good for ~1500L), this $90 system can handle bacteria, protozoa, viruses and particulate &mdash i.e. the gunky yellow stuff that came out of the spigot at our campsite (see below). The CleanStream is straightforward to use. After attaching the hoses to either end of the filter, you fill the "dirty" bag from your stream, spigot or other source (avoid shallow, still puddles!), and hang up the dirty bag, leaving the "clean" bag on the ground or somewhere below the dirty one. Instantly, gravity pulls the H2O down through the filter and into the "clean" bag. There's also a clip on the hose that lets you pause the filtering if, say, you need only a smaller quantity of water in one minute vs. three. I will admit the spigot where we were camped was unlikely to have any contaminants, bacteria, etc. However, there's something about drinking yellow water that doesn't sit too well with me. Thus, we double-filtered our water, which dramatically reduced the yellow: [Note: to avoid mixing up the bags during use, write "dirty" or "X" on the dirty bag with a Sharpie.] Gravity filters aren't new, but this was my first time trying one out*. Reason being the $90 price tag makes it somewhat of a luxury item, imho. When I backpacked Hawaii for 2 months in college all I used were $7 for iodine tablets. I drank from streams and waterfalls and never got sick, but the taste wasn't terrific and using tablets required way too much time: drop in tablets, wait 30 minutes, and then another 30 minutes if you also use the taste-neutralizing tablets (which I did not). At the time, though, the tablets were way more preferable to filtering with a hand-pump. After hiking 12 miles of rocky coastline, the last thing you want to do is expend energy just for a sip of fresh water. If you're car camping (which I was recently), you're likely partial to gear that will make the experience as cush and convenient as possible. So for $90, you can have potable water in less than 3 minutes, literally, by doing nothing. Or you could spend $7 to have potable water in 30 minutes. Or you can spend somewhere in between on a hand-pump filter and get some added exercise. Your call. *It's worth noting there are other systems some packers have been using in conjunction with Platypus bladders, including the Sawyer and Aquamira Frontier Pro. I have no personal experience with either.