These are the tennis-type balls that come with the original Chuckit thrower.  They're OK, but they don't go the distance or have the "mouth appeal" of the Ultra Chuckit ball.  My yard is littered with these balls and none of my dogs will play with them, only the Ultra ball or various Planet Dog balls.  Plus, according to The Whole Dog Journal, these colorful tennis balls are laden with chemicals that aren't healthy for your dog.  Spend the money on Ultra ChuckIt balls; They cost more but last longer, fly farther, and are easy to clean.