SportDOG Fence Transmitter - Replace the Fence Transmitter for your SportDOG Brand In-Ground Fence system or Contain+ Train system, or create a containment and training system with your existing SportDOG Brand Remote Transmitter by pairing this Fence Transmitter with the Wire & Flag Kit (SDF-WF) and the Contain + Train Collar Receiver (SDF-CTR). Expands up to 100 acres with purchase of additional Wire & Flag Kits (SDF-WF) Expands to any number of dogs for containment with purchase of additional Collar Receivers