Crush the Seeker Hydration Reservoir when empty and store in the included storage bag. The flexible design makes it so light and compact, you'll forget it's in your pack. Wide working temperature range (can be frozen - max temp 60° C / 140° F). Filter more water in the backcountry, most 42mm threaded filters (Katadyn BeFree) screw on to the top. Flexible and abrasive-resistant TPU, the Seeker can stand up to whatever you throw at it. No weird taste, and no unnecessary or harmful chemicals.