This ball came with the Zh Zhu Pet City at Christmas. I was concerned after reading previous reviews, however we have found the ball clips together & stays together well. It is a little tricky for my 5 yr old to open & close it so an adult is needed. Without the stabiliser the hamster just falls over, however if the blue plastic stabiliser is attached to the hamster it moves around for ages without falling over...our only problem is that some hamsters fall asleep very quickly in the ball & keep needing to be woken up!
Its a useful bit of kit if you have a carpet as the hamsters can move around the room...without the ball our hamsters only move inside the Pet City due to carpets.