Introducing the NEW Halo Collar 3, the Most Accurate GPS Dog Fence Available - The new and improved Halo 3 wireless dog fence system uses Proprietary PrecisionGPS AI software to leverage direct GPS signals and ignore false data. Unlike any other tracking collar for dogs, Halo uses an active GPS antenna that engages satellites to provide better reception in areas with poor coverage..Safety Everywhere You & Your Dog Go - Halo's wireless pet fence keeps your dog safely inside the boundaries that you easily define and prevent them from leaving (unlike any other wireless fence for dogs, which only notifies you when they escape). Simply draw the boundaries on your smartphone..Real-Time Tracking Keeps You in the Know at All Times - The most up-to-date real-time location tracking of any GPS dog collar available lets you know exactly where your pup is at all times. The wireless dog fence system also tracks activity and resting time, unlike a standard dog training collar..Easy Setup & Training with the Halo App - Instantly create and store up to 20 GPS wireless dog fence perimeters at the touch of a finger in the Halo app. Video tutorials guide you step-by-step through getting your wireless dog collar fence system up and running, plus built-in dog training designed by Cesar Millan..Customize Feedback to Suit Your Dog - Our wireless fence system can provide sound, vibration, and static feedback—whatever is best for your dog. Paired with your other dog training tools, there's nothing your dog can't do with Halo..Sizing Information - The Halo Collar fits dogs 20+ lbs with a neck size of 11"-15" for Small and 15"-30.5" for Medium/Large. If your dog is in between sizes, we recommend getting the larger size. Only for dogs 5+ months. Your Halo Collar comes with step-by-step instructions for how to tailor the collar to your dog for a perfect fit.