Outward Hound H2O Water Hydration Pack for dogs ~ Size Large (Ice Blue/Elephant) The Hydration Pack is the ideal watering pack for hiking or exercise. Your pet carries its own water supply on hikes and long walk. A storage pocket for gear and essentials. A wide screw top opening, it's easy to fill, close and clean. The Hydration System Dog Pack: for dogs over 50lbs. with a girth over 32"