This BPA-free, stainless-steel, patent-pending water bottle has two openings: the small one up top has a ball-bearing to control water flow when you hold the bottle upside-down for Dog to drink (think hamster water bottle and you're on the right track). The second opening is larger to allow for filling + cleaning and get this - un-screw the whole top of the bottle and flip it over - and it's a cup!