GPS Tracking + E-Collar Add-A-Dog Collar only; Compatible with the SportDOG Brand TEK Series 2.0 GPS Tracking + E-Collar System (TEK-V2LT) and TEK Series 1.5 GPS Tracking + E-Collar System (TEK-V1.5LT) Expand your TEK Series 1.5 or TEK Series 2.0 GPS Tracking + E-Collar system to track and train up to 21 dogs with purchase of these Add-A-Dog Collars Featuring HopTek technology, this collar uses GPS satelites, not cell service, to track and train your dog up to 10 miles away; It reports the direction each dog is headed, the path they took to get there, and whether they are moving or stopped With DryTek technology, this tracking and training collar is waterproof and submersible to 25 feet; Fits dogs 8 pounds or larger with neck sizes 10.75" - 23" The downloadable operating guide, and a locally based Customer Care Center, reachable at 844-209-4636, provide support when you need it By designing our products in the field, with heat, cold, rain, snow, dust, mud, and wind in mind, SportDOG Brand has become one of the most recognized brands in the electronic tracking and training categories, making the promise to create "Gear The Way You'd Design It"