The width of the hole? It's 126mm (doesn't look right but that's what the measurement says) but it's 140mm fan slot, just as Lian Li says, just fitted BeQuiet!'s 140mm Shadow Wings fan there.
The cooling is surprisingly good, a lot better than I expected.
With my previous case, Cooler Master Storm Enforcer - CPU under load = 59c, GPU under load = 80c~
With A05FNB - CPU under load = 52c, GPU under load = 75c and it's much quieter.
Looking at the results, looks a bit odd, considering the air flow used in A05FNB, I expected it to be a degree or two hotter.
Gonna make a new thread and post pictures soon. (After I've eaten something

)
Cable management without a modular PSU is a nightmare with this case ):