Professional trainers and everyday dog owners can build a better dog with the Pro 500 Plus, a simple and rugged training and tracking device. Expand your training for up to 3 dogs, using up to 18 levels of continuous and momentary stimulation, tone and vibration for effective training across the board. When your dogs are on the move, you can quickly glance at the built-in display to see which direction they're moving and how far they've gone from a range of more than 2 miles. PRO 550 Plus uses GPS and GLONASS satellite reception to lock in on the position of each collar.