FITS HYDRATION VESTS AND PACKS: Soft material and an innovative squeeze welded base create a low-profile tapered flask. Fits easily into most hydration vests, belts or pack pockets. Foldable bottle: Soft material adapts to each bag and shrinks as you drink to reduce movement and easy to pack when empty. PERFECT FOR HELP STATIONS: SoftFlasks are equipped with our SpeedFill Cap which is designed for quick and easy refilling at auxiliary stations. A side tab opens the cap in one motion and snaps close with a click. Filter compatible: compatible with 42mm threaded backcountry water filters, including UltraFlask+ filter cap. OVER LIFETIME WARRANTY: If you encounter any problem, we will repair or replace the item for free. Whatever it takes to keep your adventure going.