After testing all available 4-blade 31mm props I have learned that NewBeeDrone Azi Quad Blade Micro Propellers give me the best performance for the buck :-))) I would recommend these propellers to any tiny whoop racer or freestyler :-)

My go to props. Very durable!

they sound better then most this size

This prop performs great and is quite rigid. Unfortunately if you like to explore different motor & prop combinations, they will not survive more that one change. The plastic formula used has too much rigidity, so the shaft hole will not retain much grip after it is removed the first time. Basically you'll be afraid to change props because it will be 1-4 dollars a shot, quite expensive!

I asked for these as a replacement and they arrived incredibly quickly and work really well. 4 stars!