Super Pet Flat Bac Water Bottles have been specially designed to be the best quality water bottle for small animals. Every Bottle comes complete with the Snap-Lock bracket that securely attaches the water bottle directly to any wire cage, yet is simple to detach to make refilling fast and easy. Sold separately, Super Pet's Suction-Cups can be inserted into the Snap-Lock bracket allowing you to secure a Flat-Bac Water Bottle inside any glass enclosure. Plus, only Flat-Bac Water Bottles have the original Floating Duck refill reminder. 4oz. Bottle is perfect for dwarf hamsters, mice, hamsters and gerbils. 8oz. Bottle is perfect for hamsters, gerbils and pet rats. 16oz. Bottle is perfect for guinea pigs, hedgehogs, pet rats, ferrets, dwarf rabbits and chinchillas 32oz. Bottle is perfect for rabbits, ferrets and chinchillas.