In the product packaging there was no guidance, this I have found after mounting on the invoice.
The old glass was cracked after a fall (on carpet). I can not judge whether the display otherwise would have taken damage, but with the glass I feel safer. The old glass had after nine months, no significant scratches o. Ä.
I have the old glass removed during installation and the new bonded directly to the dust-free surface. Better it would have been, the display in between still einemal to clean (with a lens cloth?), Because apparently were from the old "bond" or residue on the screen that you can now see a slight streaking under the glass. Annoying.
