WTF Wild Turbo Fans For ESC 25MM Version make a great choice when needing a fan upgrade on your ESC.
25mm Ultra High Speed - ESC Cooling Fan
With racing ESC operating in extreme electrical current and temperature, we have created a more powerful fan for high power ESC, with RPM in the 20,000 range @7.2V
 
Size : 25mm x 25mm x 10mm
Operating Voltage : 6V-8.4V
RPM Range: 6V - 8.4V 18000 ~22000
Current @ 8.4V: ~0.43A
Axial option: Available in ball bearings
Plug : Hobbywing V3.1 style