Osprey hydraulics 500ml softflaskthe hydraulics 500ml softflask from osprey is the perfect answer for staying hydrated when out and about the flask is extremely lightweight packs down when empty and fits comfortably inside your backpacks stretch mesh pockets simple hydration solution the combined sports cap which is included is ideal for quick handheld hydration while the extension hose also included is ideal if you are using the hydraulics softflask in your backpacks harness pocket it