The kong tennis balls are seriously less affected than regular tennis balls and twice the price. My dog managed to sneak one of the brand new tennis balls while I started up my car for work, as I returned back inside the ball was ripped to shreds in then 5 minutes.. whereas a normal Wilson tennis ball would have lasted at least a day.. Don't waste your money on the tennis ball type by the black rubber one If your dog is a heavy chewer.. I honestly think I may contact the company and get a refund on the tennis balls to upgrade to the black rubber one as recommended by other dog owners.