Ideal for longer expeditions like ultra-trails, the SOFT FLASK 500ml/17oz XA STD 42 filters bacteria and protozoa from natural water sources, so you can drink easily and safely without needing to carrying huge volumes of water. Shrinking as you drink to limit water bounce, the flask lets you know exactly how much you have left. Filtering your water on the go means you can carry less water, and therefore less weight, while you run to help reduce fatigue. The 500ml soft flask features a high-flow valve and wide 42mm cap for easy refills and drinking. The filter removes bacteria and protozoa from approximately 1000 liters of water to help keep you hydrated and healthy, however remote your destination. Eliminates 99.99% protozoa, Cryptosporidium oocysts, and bacteria. Filter included Use to refill your bottles or hydration reservoir with clean water. Large 42mm opening makes it easy to fill with ice or energy mixes Meets the US FDA Standard testing protocol 100% BPA & PVC free High-flow va