The Sawyer Point Zero Two Purifiers features a 0.02 Micron Absolute Hollow Fiber Membrane. To use the Sawyer Point Zero Purifier simply follow the instructions enclosed and affix the purifier to any bucket or pail to yield bacteria-free water in remote locations. The only external force required for the system to function is gravity. The flow rate of a purifier is determined by a combination of head pressure, altituted and how clean the filter is. Absoulty no chemicals needed and is rated for One Million Gallons. Sawyer is confident in their one million gallon claim because you can continually clean the filter by backwashing it with clean water. Backwashing is not required often unless you are filtering very turbid water. Backwashing is as simple as reversing the filter flow with clean water. Forcing the clean water back through the filter flushes out all of the contaminants and only takes a few seconds. NO REPLACEMENT FILTERS OR CARTRIDGES ARE NECESSARY. We trust you will thoroughly enjoy the ease and extra protection this proven next generation technology offers you.