Give yourself peace of mind during backyard play time with the PetSafe Stubborn Dog In-Ground Fence. Create a secure 1/3-acre boundary to give your best friend freedom to explore. The included Heavy Duty 16 Gauge copper wire, encased in a 45 mm jacket, provides added durability so your fence will last for years to come with little or no wire repairs. If you want to contain a larger area, the system is expandable up to 25 acres with the purchase of additional wire and training flags. The receiver collar features 5 levels of correction at our highest intensity for the most persistent pups, including a tone plus vibration mode that is perfect for hearing-impaired dogs. The collar is designed for pets 8 pounds and up and adjusts to fit neck sizes between 6-28 inches. If you have more than one dog, you can contain an unlimited number of pets by purchasing additional PetSafe In-Ground Fence receiver collars. PetSafe brand is here to help you and your pet live happy together. What's Inside: • Transmitter with power adaptor • Stubborn Dog receiver with adjustable collar strap • Surge protector • 500 ft. of 16 Gauge solid copper wire • 50 training flags • 9-Volt battery • 50 training flags • Waterproof splice capsules and wire nuts • Short and long contact points for short or long-haired pets • Test light tool • Product Manual • 1 year warranty