New in box! Create a safe outdoor area for 2 dogs without a physical fence. Easy to install. Receiver collars have a tone only mode and 2 levels of safe, static correction that you can adjust based on how your determined dog responds during training. The Stubborn Dog Fence Receiver Collar is waterproof and comfortably fits dogs 8 lb and up and adjusts to fit neck sizes 5-25 inches; For dogs 6 months and older. Create a safe 2/5-acre play area for your best friend with the included 328 feet of wire.