What are these black stickers in my oneplus one for?

Hi, a week ago i bought an oneplus one middle frame for my oneplus one. Today the screen arrived and i started to repair my broken oneplus, when i was in the reassembly process I found out that the new middle frame came without some black stickers so i proceeded to take them out from my broken frame, this is what I'm talking about:

I think this must be something relationed with the anntenna of the phone, am I correct? Where can i get a replacement for these stickers?

Thank you in advance