Haha, this is super black powder maker after you play it.
I have a client who looking for supercheap flatwound bass string several years ago, and I found this on AliExpress.
String construction look fine when open box, but there are some diesel like smell rather than metal smell. Once setup done and tune in pitch, all my finger get black just play no longer than 10 minutes.
After a week, my client told me that black power still there but decrease in some amount.
Bass tone after a week sound like fresh set flatwound, even sound fresh, but the tone decay quite fast.
Need to mention that the E string sound much better than dull and lifeless GHS flat E string .
Already forget those string tension, balancing and plucking feel.
Hopehelp