Sawyer’s 4-liter dual bag portable ultra purification system physically removes viruses from water. This system allows you to effortlessly purify 4 liters of water in as little as 10 minutes. Use this system for one person or a group of people. The convenient bag to bag gravity system doesn’t require any pumping. Simply fill up the grey reservoir with unfiltered water, attach the filter and tube to the clean blue reservoir and gravity does the rest. Once the blue reservoir is full hang by its handle to fill water bottles, containers, and pots and pans from the high flow .5 liters per minute dispensing cap. Bladders are 20-inches x 10-inches each. Included in the system is a drink tube for attaching to the bite valve of your choice (sold separately) so that you can use the reservoir as you would any hydration system. Perfect for hunting, camping, fishing, disaster relief and emergency preparedness kits or on adventure travel where potable tap and bottled water are not easily carried or safe to drink.