Get more MINIATURE iFetch balls for more fetching fun! Features: One order of iFetch balls will include 5 balls. iFetch balls are manufactured for optimal operation with the iFetch ball launcher. iFetch balls are 1.5" (40 mm) in diameter and are not full sized tennis balls. They are designed to be used by small to medium sized dogs. Owner supervision is recommended. Some similar pet balls (40mm or 1.5" diameter) will work. You can find out more by contacting iFetch. Some balls, even if the right size, will not work or may be hazardous when launched. Some dogs slobber more than others. If your dog is a heavy slobberer the iFetch may require wiping off balls from time to time, making it difficult for the dog to play continuously by itself.