Ø 4 cm: The KONG AirDog Squeakair Ball combines two classic dog toys: the tennis ball and the squeaker toy: to create the perfect fetch toy. Our durable, high-quality Squeakair Ball will not wear down a dog’s teeth. It’s made with a special nonabrasive felt, compared to the abrasive material on normal tennis balls: Perfect for games of fetch: Squeaker to induce play: Nonabrasive tennis material will not wear down your dog’s teeth