rubber grommets

Gigabyte C200 case has screw has a missing rubber around it is that safe for the glass? I have been overthinking about it and it annoys me. The screw thumbscrew is with me its not missing but the rubber around the screw house/hole (that the glass rests on from the top right spot as you can see)...

I have an MSI MPG GUNGNIR 111M case that only came with 3 trapezoid-shaped rubber grommets. However, the case has a total of 7 trapezoid-shaped holes and I would like to purchase 4 more trapezoid-shaped rubber grommets. Any assistance would be helpful!