Using the advanced technologies of the original Guardian purifier, this gravity-powered MSR Guardian Gravity Water Purifier has you covered with safe water around the world—from your local backcountry to remote villages. Hang it while you go about your tasks at the hostel, basecamp or campsite. Its 10-liter reservoir supports the daily water needs of multiple people. Originally designed to protect service members in the field, this rugged purifier handles the abuse of travel and meets the NSF P248 military testing standard.  For optimal flow rate, hang the reservoir bag at least 6 ft. above the clean water receptacle.