The PetSafe® Refurbished 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 your pet in 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 including a tone-only mode. 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 6-26 in. You can add an unlimited number of dogs to the system by purchasing additional compatible PetSafe® In-Ground Fence receiver collars.