What are the rubber circles for on the back of my pc case? Should I just leave them like that if don't have a need for them? Or are they likely to let I'm dust into the motherboard?
Edit: thanks for all the replies, so just for water cooling I have no need for.
There were some old PCI cards that were very badly designed, and they required things plugged into them from inside the case, or they needed to plug into things on the motherboard. I had card that controlled Cold cathode tube lighting that could also connect to audio to sync to the music that worked that way
But, the actual answer is that the grommets are for old-school water-cooling.