Dunno where else it is used, but on my "Best of... James" CD the disk itself is held on a simple foam disk a couple of mm high. This appears totally unbreakable and much more secure than those poxy plastic spigot thingies that where obviously invented by the same man as did the dreaded "tetrapak" ....... (rant over).

Anyway, little foam disks - that's where it's at

PS: I think they have a patent on it (go figure!) so don't go mad and use this feature commercially.