I found that units that are made of silicon (Cage and u-ring) to be almost pointless. Because of the flexibility of the material and simple biology, getting out is super easy.
We tried an imitation CB6000s for a while to get a feel and it was a great experience. Briefly played with the Dominix cage from LH, but after some painful experiences with it had to return it. The official CB range has the a rounded u-ring which I understand is far more comfortable. (Mine had a flat edge, like a rounded H-beam, so there was a tighter fit.
I had to give up on that as a fetish because it was causing me to many problems in the basement. All I can say is do your homework before you commit, that is one area you don't want to damage.