Material for sealing around ventilation duct.

[Serfi]

The previous owner of the house had just installed FTX ventilation. Some walls where the ventilation ducts go through don't look nice. In the picture, it's a concrete wall. Since it's the first house I live in, I'm wondering what material should be used to seal around the pipes. See image.

 

[Acido]

Cover plate!

https://www.luftbutiken.se/tillbehor-friskluftsventiler/3409-tackbricka-160mm.html

And some soft sealant before you put on the ring.