While both have the bead or ball, in CBR the bead has depressions on its head to take the ends of the ring, so that they fit into it snugly. In the Ball closure ring, it is a full bead and the ends of the ring hold it.
The reason for this is the following – most ball closure rings are large gauge, and it’s technically much easier to make them as BCRs rather than CBRs! ❗
It is good to know the difference, even though you will come across the two names being used for the same jewelry. Some people even claim that CBR is American while BCR is European. Now you know the real difference between the two – but anyway – in the real life you’ll hear both BCRs and CBRs referred to as captive rings. 😉