Aurora R8, replace CPU fan

The CPU fan uses Intel standard 75mm hole spacing to mount to the motherboard. 

You're likely to get a boot error if you change the fan to any other 4 PIN PWM fan.  The bios is programmed to check for proper fan responses to pwm (per the OEM fan). 

You're want something under 70mm in height (assuming no room for airflow) and conforming to the Intel keep out zone (100mm) unless it clears the RAM.  An example of something that would fit is the Cryorig C7 copper. But note the fan error issue.  

I believe the Nidec Gentle Typhoon will also work, although its much less popular than the ML120 pro. 

Case fans are 120mm. 

For case fans, a 3PIN fan or a Corsair ML 120 Pro (to avoid the start up error noted in my prior post).