The PetSafe® Refurbished Stubborn Dog In-Ground Fence™ System allows you to create a safe and secure boundary around your yard to give your pet freedom to play and explore. You can create up to a 1/3-acre boundary by burying wire around your desired containment area. If you wish 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 including a tone plus vibration mode. The vibration mode is ideal for training hearing-impaired dogs. The low-battery indicator on the waterproof receiver collar will let you know when to change the battery. The collar is designed for pets 8 lb. and up and adjusts to fit neck sizes between 6-28 in. You can add an unlimited number of dogs to the system by purchasing additional PetSafe compatible In-Ground Fence™ receiver collars. This fence is compatible with all PetSafe® In-Ground Fence™ receiver collars except for YardMax receiver collars.