thanks flip, I have heard so many things about tennis balls and now you have put a new spin on it. First I heard that the glue used to glue the felt was a problem, and then it was the dye, next was the felt is abrasive on their teeth, now you tell me that it is the rubber. I guess I should just except that it is not good to let them play with tennis balls for long periods but I am still curious to know the real reason.
jen