Chuckit! The Whistler Ball Rubber Fetch Dog Toy Medium (2.5 ) for Dogs 20-60 lb Assorted Colors Pack of 2 - All of the Chuckit! balls are specifically designed for the most demanding use by a growing population of fetch enthusiasts. Each ball is compatible with the Chuckit! launchers so that you do not have to bend down and pick up a slobbery ball. Whistler Ball - Designed for the most demanding use by a growing population of fetch enthusiasts this ball twitters and whistles in flight.