The lightweight yet rugged blue bottle has numerous clever design touches. The 0.2-micron filter element is based on “hollow fiber technology.” These perforated straw-like segments screen out pathogens from rivers, streams, lakes and puddles, removing them from the water. All you have to do is suck on the straw. A lack of moving parts and a lack of noxious chemicals provide real advantages to this design. Just fill up the bottle, screw on the lid (which contains the filter), and drink through the flip-top drinking tube. The only maintenance is a simple “blow-back” procedure. After drinking each bottleful, unscrew the lid and blow through the filter to back flush it. This is the easiest water filter I’ve ever used. It’s perfect for both a day hike or a full-on bug out bag.