This equipment is the perfect way for you to introduce your dog to fly ball and have fun in your back yard. Fly ball is a team sport with four dogs on a team. The object is for your dog to go over four hurdles to reach the fly ball box. There they step on a pressure plate that triggers the release of a tennis ball. Ball in mouth, the dog returns over the hurdles, and the next dog takes his turn. The fly ball box does not throw the tennis ball into the air.