PetSafe Stubborn Dog In-Ground Dog Fence - 1000 Feet of 14 Gauge Upgraded eXtreme Wire 1000 Feet of eXtreme Brand 14 Gauge Wire Upgrade, for 20+ Years of Reliable Performance Without Degradation Solidly Built and Geared Toward Stubborn Dogs 50+ lbs., Compatible With PetSafe Indoor Pet Barriers, Unlimited Dog Capacity (With Purchase of Additional Collars) Can be Expanded to Contain up to Up To 25 Acres With the Purchase of More Wire Expandable Electric Fence System Can Accommodate Any Number of Dogs with the Addition of Collars Unique Correction Levels for All Dogs on the System (5 Progressive Plus Tone and Vibration)