This gravity-powered water purifier uses an advanced ultrafiltration membrane that removes 99.999% of viruses, 99.9999% of bacteria, and 99.99% of protozoa. The LifeStraw Mission requires no electrical power, batteries, or replacement parts. Just fill the BPA-free 12-liter bag according to the fill-marker water level windows and then hang up the bag. The LifeStraw Mission produces a flow rate of 9 to 12 liters per hour, filters up to 18,000 liters (4,750 gallons) of water, and can even handle turbid and muddy water. The roll-top dry bag is lightweight and easy to fill, and the purifier is simple to clean in the field using the integrated back-flush bulb.