I got my delivery 2 days ago and put it to the test last night. The results are not great. I used them to sand a little beech vase, about 6" tall and 2" diameter. OK, this wood is hard and it's got knots. However, the first 50mm disc of 120grit lost it's teeth within seconds, the second held out a little longer. Sanding the outside with a rotary inertia sander, it took a lot longer to do the rough sanding with 120 than it ought to, and the 320grit disc separated from its backing within 10 seconds of usage.
And to top it all off, when I moved my banjo across the bed, it create scratch marks, so clearly the bonded abrasive had become unbonded and ended up on my lathe bed.
Sorry guys, I am not impressed. I will use it, but will probably not buy again.