Failed at holding air...before put into tires
I got these on Chainlove and thought it was a good deal. I mean, tubes are tubes, they hold air, they go into tires, that's it, right? I ride tubeless on all my mountain bikes anyway so these are really only for backups.
I discovered, however, at a race when I lent three of these to teammates that all three of them did not hold air; they all had significant splits along seams. In fact, one of my teammates did get a flat that race and had to walk most of the course because the tube didn't hold air. We only discovered the other two didn't hold air when we got back after the race and inspected them; luckily no one actually needed one because they were worthless.
So...three out of four don't hold air right out of the package. That's just unacceptable. Tubes are easy, they should work.