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.
Besides the water cooling that's already mentioned, those could be used for example for routing an internal device out and into the I/O of the motherboard. An example would be some fan/RGB controllers that are meant to be somewhere inside the case, but are terminated with a standard USB A plug (and very few motherboards have that as an internal connector). Another example is a mini display that you could put inside the case that would need to interface with the GPU (so you'd need to route a DP or HDMI cable out of the case and into the back of the GPU).