Question : Problem: Looking for a fan to place on top of Dell Rack

Hello,

I have a 24U Dell Server rack that is crammed full of equipment.  The top of the rack has two circular holes in the back that are roughly 4.25" in diameter.  I am looking for some type of fan or fan system that will pull the hot air in the back of the rack out these two holes on top.  I can't seem to find anything on Google.  

Thanks!

Answer : Problem: Looking for a fan to place on top of Dell Rack

if you take a look here:  http://www.pctoys.com/cadu80fancok.html   you'll see the unit has round fal holes and 4 screw holes which allow for screwing in to the square housing of the fan. The hole can be covered with a fan guard which also lines up with the screw holes. This is usually the standard for fans in all electronic equipment.
Are you sure it takes a ifferent type of fan?