"Add to your Dogtra PATHFINDER2 GPS Dog Tracking and Training System (not included) with this additional Dogtra PATHFINDER2 TRX GPS Collar. The PATHFINDER2 system supports up to 21 of these dog collars. This collar features an LED locate light and a GPS tracker to help you track your dog. The collar works within a 9-mile tracking range and is waterproof. The minimum neck size is 12"". This collar is built for dogs above 35 lbs. PATHFINDER2 GPS Connector (not included) required to operate collar. Part of the PATHFINDER2 GPS Dog Tracking and Training System (not included) Requires PATHFINDER2 GPS Connector (not included) Waterproof LED locate light GPS tracker Works within 9-mile range Built for minimum 12.5"" neck size and dogs above 35 lbs."