I've had this tower for my 2 cats for over 6 months. But just recently I woke up in the middle of the night to hacking, only to find one cat with the ball and string attachment, wrapped tightly around his neck, unable to move from the platform he was on. I quickly cut the string and he was alright but I'd hate to think of what would have happened had I not been homewoke up. I will not be replacing the ball witht he second one provided. So I'd be careful with the toy ball attachment.