It was amazing how fast the dog caught onto the invisible fence. He only crossed it once and was a completely changed and much calmer dog after that 1 incident. Wherever he saw the white flags he wanted to leave a healthy buffer between himself and the flags. They live close to the road so it was an issue of keeping him safe and off the road. The system they bought had multiple correction levels.He's a big black lab but he has a ton of respect for the invisible fence.