To correctly print the cover and case inlay, set whatever software you are using to print them to proportional printing, then set the height for the cover to 11.9 cm, and the height for the inlay to 11.7 cm. This should ensure that the width automatically sets itself correctly.

If you have a transparent CD tray, here is an image to go inside the tray.

And here is the CD label courtesy of Colin Gunn...