Question What are these called?

[Locas]

My corsair cooling system is clamped to my cpu via a bracket that has 4 of these tightened onto a thread.

https://imgur.com/toanJFo

View: https://imgur.com/toanJFo

 

[kanewolf]

Cap nuts would be the generic term.

You could also look at the installation instruction on your cooler to see what Corsair calls them. On an H100 for example they are labeled "thumbscrews"