Stainless-steel Dog 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 and cleaning. You can also un-screw the whole top of the bottle, flip it over - and it's a cup! Stainless steel construction. BPA-Free. 16 FL-ounce. Fits most standard cup holders. Comes with handy carabiner for easy carrying.