There are two 3" holes at the top, 2 behind each amp and larger component for vent and wire, also 3"Not long ago there was a thread here about fans, 8" I think. I finally decided to place on on each major component, 4 in all. While the fans ate quiet in free air, once you place it on the component even with those double sticky foam is the same so I need to shut the doors. The mag latch at the bottom is one of those push to release so one is shut the other is open but held by the magnet. The crack is more than enough to keep everything cool. There is space above the cabinet and behind the component cabinet. Curved stairwell on the other side.
Here is a pict of the fan:
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