The PetSafe YardMax Rechargeable In-Ground Fence allows you to create a secure 1/3 acre boundary around your yard to maximize your pet's play space. Traditional in-ground fences correct your pet before they cross the boundary which limits their play area. With the YardMax In-Ground fence your pet receives correction after they cross the boundary which gives them 30% more play area. Unlike traditional in-ground fences, your pet will not receive correction when they come back into the yard if he passes the wire. This underground fence is expandable up to 10 acres with the purchase of additional wire and training flags. The rechargeable, the waterproof collar features a sound-only mode for training plus 5 levels of adjustable correction depending on your dog's temperament. The collar adjusts to fit neck sizes between 6-26 inches and is recommended for pets who weigh 5 pounds and up. Whether you have one pet or several furry family members, this in-ground fence will contain as many pets as you need with the purchase of additional YardMax Rechargeable In-Ground Fence Collars. Compatible with: Pawz Away Indoor Pet Barrier (ZND-1000, ZND-1200), Pawz Away Outdoor Pet Barrier (RFA-378, PWF00-11923), and Pawz Away Mini Pet Barrier (PWF00-14040, PWF00-13665).