Platypus Cleanstream Gravity water Filter. Fill it, hang it, forget about it. The CleanStream Gravity Filter is the Platypus answer to simple, effective and fast water filtration. The revolutionary Hollow Fiber media filters 4 liters of water in just 2.5 minutes without a single pump stroke. Simply fill up the Dirty 4L reservoir, connect it to the rest of the system via the handy quick-disconnect fitting and hang the whole system from a tree, your car, or anywhere. Then go and cook dinner, chat with friends, set up your tent or whatever. With no moving parts you get a quick, 4-second clean by simply reversing the height of the reservoirs and a full 8-liter capacity provides on-demand water for any group size. The system includes two 4-liter reservoirs (one for Dirty, unfiltered water, one to collect Clean Filtered water), Hollow-Fiber Filter Cartridge, hoses and all fittings.