My Axel destroys tennis-balls like its nothing, the only other toy that I have been able to find that withstands his jaws are Kongs and ropes. But he gets bored with them, and can some how untie the ropes. We have tried the Kong Wubba, and that lasted awhile, but when it ripped and he saw the tennis-ball, it was over. So we bought him another one, and he knew that there was a tennis-ball in it at the top and destroyed it in about half an hour. So we moved to the Kong Tails. Which was alot better, but he still has no intrest to play with it as much as he does with any type of ball. We have tried every type of ball, and he destroys them, any suggestions on a ball that won't break and can withstand his jaws? =)