tecnolgy
The hole in the CD is where the machine you put it in "grips" the CD so the disk can be spun and thus read and used.
The small hole at the center of a CD is called the "spindle hole" or "hub hole." This hole allows the CD to be securely attached to the spindle of a CD player or drive so that it can be properly read and played.
So they don't fall out of the CD player
it is 5 .5 centermeters long exactly
lumen?
A shape with a hole in it is called a "torus." It resembles a donut-shaped figure, with a hole in the middle that runs through the center.
They are called man holes, or manhole covers.
After MUCH research looking for the answer to this myself, I have found that the parts are called either CD hubs or CD spiders. They are the "bump" that fits into the center hole of the CD and holds it to another surface when you are not using a case.
On the face of the cd player, look for a small hole. With the power off, insert a paperclip in the hole, turning the gears to push the cd out of the player.
most CD drives have a tiny hole near where the CD goes in, just stick something in the hole, like a paperclip or something. Push it into the hole and it will force the CD out. It might not have the hole, I think only computer style CD drives have it.
It is just a clever name for a CD case. They are the slimmer version of the standard CD case. "Jewel" refers to the piece that clips into the center hole of the CD to keep it in place. It has a jewel-like design.
CD's have a diameter of 5.5 centimeters;)