It could be thermalright X Silent fan... The default fan which comes with MUX 120 comes with the following specs
Fan Rated Speed: 600~1300RPM
Noise Level: 17~25 dBA
Air Flow: 26.6~57.6 CFM
More interested in what is the custom fan the review uses. And which fan the author speaks of as the one he is going to use on his MUX 120. Sounds like the custom fan is a 140 mm.