Collapsible by nature, the Platypus Water Tank Replacement Reservoir packs flat for efficient packing and our Big Zip opening makes filling and cleaning a breeze. The biggest, 6-Liter tank weighs a mere 4.4 ounces (124g), making it just as practical for group backpacks and river trips as it is for summers on the road. New features include our new, more durable film, a lower, more stable design and reinforced handles for easy carrying.