One of my favorite 120mm fans I have
I got this fan from PC Hub.com for $14.69
The fan has 9 blades and 11 back vanes. I really like vaned fans, since they work better than other fans for most applications. The vanes focus the airflow into a straight line.
Time for disassembly
The fan uses 2 NSK ball bearings, with a spring-washer-clip holding system. The 3-phase brushless dc motor has 12 coils and 8 poles. This gives it twice the power of a similar sized single-phase 8 pole motor, and a 20% increase in efficiency as well.
P. S. Hard-drive motors also typically use 12 coils and 8 poles. Most hard-drive motors are also made by Nidec. Just a thought on possible similarities.