SpotOn should be fitted to your dog like a regular collar. Use the adjustable strap so it fits snugly but lets you comfortably fit two fingers between the collar and your dog’s neck. When properly fitted, the GPS antenna should sit on the back of the dog’s neck so the GPS icon is facing the sky. Tuck any excess strap underneath the collar. Once you’ve found the proper fit for your dog (and if your dog is fully grown), you can trim the excess collar strap. If the collar doesn’t fit please give us a call at 1.603.488.1504 or email us here.