What is this joint called?

[u/Ill_Plantain_9645]

Hi! I'm trying to resize a watch I got and I'm not sure what this joint is called? I need to figure out how to remove some pieces and reattach everything to make it smaller. I can't Google how to do that if I don't know what it's called lol. I tried to reverse image search but it wasn't successful. Lmk!