Let your outdoor dog "pull his own weight" with the Kyjen Outward Hound Quick-Release Dog Backpack. Lightweight, with an adjustable harness and removable pack, it provides maximum comfort and convenience for your dog when hiking. Large, extra-strong, tear resistant nylon storage pockets hold food, water and other gear. Also features reflective safety strips along both sides of the bag. Also features a Quick Release Leash Holder for use when approaching other hikers, dogs, or wildlife. Small is recommended for dogs weighing up to 18 lbs with a girth up to 25" Medium is recommended for dogs weighing 18-50 lbs with a girth of 26-32" Large is recommended for dogs weighing 50-79 lbs with a girth of 30-40". Extra Large is recommended for dogs weighing over 80 lbs with a girth of 36-40" (measured around the widest part of the dogs rib cage).