Note: They are not foldable!

Link:
https://www.masterairscrew.com/products/dji-spark-stealth-upgrade-propellers-x4-black

Review:

Hello and good day jh8. Thank you for sharing these videos with us regarding the Master Airscrew Stealth Low Noise propellers for the DJI Spark.  Just a friendly reminder that 3rd party accessories or devices might cause harm on the DJI Sparkr and can void the warranty as well. Have a safe and happy flying always.

Nice to see, thanks for sharing

The volume is the same - the pitch is slightly lower.  Pretty marginal improvement. IMHO
Some find the slightly lower pitch to be an improvement - placebo affect maybe?
Although alternatives/choices are nice.  Someday when the Spark is so legacy that we are the only ones still flying it those may be the only props available...
Maybe I'm just tired tonight

DJI Stephen Posted at 8-9 07:54
Hello and good day jh8. Thank you for sharing these videos with us regarding the Master Airscrew Stealth Low Noise propellers for the DJI Spark.  Just a friendly reminder that 3rd party accessories or devices might cause harm on the DJI Sparkr and can void the warranty as well. Have a safe and happy flying always.

Master Airscrew has been in the RC industry decades before DJI existed.  I recommend DJI form a partnership and officially approve their products.  Would benefit both companies.

fansc2f5448f Posted at 8-12 21:38
Master Airscrew has been in the RC industry decades before DJI existed.  I recommend DJI form a partnership and officially approve their products.  Would benefit both companies.

Hello and good day. Thank you for sharing this information and your insights with regards to this matter. Let me please forward this information to the designated DJI department for further development. Thank you for your support.

I wonder how much stress to the motor occurs when a non-foldable prop hits a fixed object versus the OEM prop.  Seems like the foldable hitting a bush or tree branch would cause less damage to the motor.