Lighten your load and drink right from the source. Hydrapak took their go-to flask and added filtration to create a system that delivers hydration without contamination. The filter — light and compact — screws on top so you can drink right from the flask. Or — if you’re carrying more water — use the system to fill a bottle or reservoir. INCLUDED BACKFLUSH ADAPTER: Plugs into filter valve and threads onto a HydraPak Stow or bottle of clean water for backflushing the filter to restore its flow rate. VEST PACK FIT: Soft material conforms to most hydration packs and larger vest pockets for a secure and stable fit. The integrated filter removes Escherichia coli bacteria, Cryptosporidium parvum cysts, and Giardia Lamblia from approximately 1,500 liters of water at a rate of >1L per minute.* Minimal design and lightweight materials make this filter the ideal choice for runners. It takes up no extra space when stored or threaded directly onto a flask. Easy to drink bite valve auto-seals after each sip, eliminating annoying drips. Filter Weight: 36 g / 1.3 oz Filter Dimensions: 42mm Capacity: 500 ml Weight: 65 g / 2.3 oz Dimensions: 240 mm x 70 mm / 9.4 in x 2.8 in Material: TPU, Silicone POM, Hollow Fiber, ABS Care: Avoid freezing filter. Freezing may ruin the hollow fiber membrane. If in freezing conditions we recommend you keep the filter in your pocket or near your body to prevent freezing.