A standard 120mm square fan from the same manufacturer at 25mm thick will have less pressure and CFM than one 38mm thick as long as the RPM is the same. The blade design/thickness would change of course.
If I saw a 220x230mm fan dimension I'd say it's a typo error.
I agree with Conumdrum that it is probably a typo. The 25 is the thickness. Most fans are 25mm thick. The 38mm ones move more air, but may not fit, so measure.
Indicentally, I just installed a Scythe Ultra-KAZE 38mm fan into my RC-690, and I haven't reached a verdict on it yet. It is super-quiet, but does not move a lot of air. It's supposed to spin at 1000rpm, but Abit uguru has it pegged at 660 no matter what voltage in the range of 8.5v-12v I'm feeding it. I can barely feel the air; it won't "float" a piece of paper put over it. I'm going to use its adapter and plug straight to my PSU, but the mobo header was working, as this fan was a replacement for another that was getting noisy.
Hey Guys! It is not a typo. There are case fans 200mm and above that have elliptical "frames" or rectangular "frames" instead of square ones. Another way to put it is that the "frames" on two opposite sides are thinner. They are made that way so that they can fit inside a pc case. Some of the larger CoolerMaster case fans are like that.
EDIT - Here's an example of Antec and CoolerMaster "odd shaped" fans:
jtt283 - I've never seen an odd shaped or odd sized 120mm or 140mm case fans either. I have seen a couple of small 40mm fans designed for chipset heatsinks that were kind of odd.
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