The PetSafe Stay + Play Wireless Fence lets your pet enjoy their boundaries at home or away. How it works: Plug the Transmitter into an electrical outlet close to the area where you want to contain your pet. Adjust the boundary from 5' to 105' in all directions. The pet area is a circular boundary. System includes: Transmitter with power adapter. Receiver collar for neck sizes 6"-23". Receiver charger. Operating and training guide. 50 training flags. Test light tool. Long and short contact points. Contact point wrench. One year warranty You can add-a-pet with additional receiver collars. Just check the model numbers