Those are indeed full-size tennis balls. As far as her size, it's kind of a funny story. I swear I measured her about a month ago and she was UNDER 16", but I don't have a wicket so I don't have an official measurement, just my guestimate. We had her measured on Sunday, and he said 16 3/4! I was like, no way. We took her back and she measured 16 1/4, then 16 on the dot. We were hoping to get her to measure under 16 so we could have her be a 10" height dog. I measured her again using my yard stick the other day, and she's at 16.. I don't think we're going to get a lower measurement. She must have had a growth spurt!