PLEASE! DO NOT USE TENNIS BALLS AS TOYS! Our Welsh Corgi made "bald balls" by tearing off the fur. He swallowed 1/2 of a "bald ball"-- perhaps after being sliced by a lawn mower. It did not show up X-ray. Finally operated. He ultimately died of peritinitis. Pass this warning to all you can. We just lost another Corgi about the same way, except this obstruction was scar tissue or tumor, blocking entrance to colon. Again, peritinitis was the complication.