Using the advanced technologies of our original Guardian purifier, this gravity-powered sibling 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 L reservoir supports the daily water needs of multiple people. Originally designed to protect servicemembers in the field, this rugged purifier handles the abuse of travel and meets the NSF P248 military testing standard. MSR - Guardian Gravity Purifier