Puribag Adventure Bladder: 2 Liter Hydration Bladder with FilterKey Features: Dual Use: This water storage bladder not only holds water but also offers effective filtration. You can use it with or without the hollow fiber membrane filter, depending on your water source. Compatibility: Easily replace the internal bladder in your existing hydration vest or backpack with this upgraded option that provides filtration capabilities. It can also be used as a standalone water bladder for maximum flexibility. Filtration &