It is a trim for the methacrylate that covers the speakers of an arcade machine.

You can see in:
https://www.youtube.com/watch?v=NFlyAQNa4Hs

I suppose that it can be used as a stiffener for any object that you want to cover, since it can be resized.
I have posted the originals in case someone wants to modify them.

Creality

Ender 3

No

No

0.2

0.4