The E-Collar Technologies PE-903 3 Dog Pro Educator 1/2 Mile Advanced Training System is a modern e-collar designed with safety in mind. It features a maximum stimulation setting and lock and set feature to prevent accidental overstimulation of the dogs. The convenient transmitter can control three dogs at once, and the medium range trainer is loaded with unique features. The bar-shaped transmitter allows for easy operation and discreetness when needed. The small receiver size and weight provide plenty of stimulation for most dogs, and the COS control of stimulation technology ensures clean stimulation without head jerking. With the boost feature and adjustable stimulation levels, this training system is perfect for advanced dog training.