What does the black gray plastic stick on LCD display assembly back

Hi, my phone is nokia 7 plus but I cannot find in the device list. Nonetheless, I find that all nokia android phone have this black gray plastic like the red box on the above picture.

Could anyone tell me what it is and use for? Because I had broken original one when I was replacing battery lol. I'm considering do I need to buy new one but don't know the keyword to find...