I have 4 fans from server "roof". They are about 12cmm, but i will have to measure then to make sure... Anyway, they are not separate fans. You plug all 4 of them in a chain to the WALL. My guess is that they are crazy fast and loud (considering power requirements). Will try them tomorrow. I just want to know if anyone needs something like that. Oh, and there is a wire for grounding, I guess, that would be your case or something else.