Like all Living WorldŽ accessories for small pets, Eco+ Water Bottles include innovative design features that meet the natural instincts of small animals and cater to their specific needs. For example, the water bottles have a double ball-bearing, drip-resistant tube with water level indicator. Plus, they are made of eco-friendly recyclable glass that is safe and very durable. They all come with a secure and easy to install spring attachment and hanger. 355 mL (12 fl oz).