Whether you want to carry the flask or slip it into any hydration vests or packs, this 17oz soft flask is the perfect hydration add-on for runs that require a bit more hydration. The bite top feature allows you to control of where your water or liquids go – straight into your mouth and not dripping out the top. LOW PROFILE DESIGN An oval collar and smaller cap create a streamlined, low-profile shape that contours comfortably to the body when used in hydration vest mesh pockets. SIMPLY COMPATIBLE Works great with all NATHAN hydration vests, packs, and wide compression belts.