Works great, much cheaper than similar products from certain luthier's shops.
My only (very slight) complaint is that I would personally have preferred to have a separate block for each radius. In a busy workshop everything that CAN go wrong WILL go wrong sooner or later. I can easily see someone sticking the sandpaper on the wrong side in a hurry and completely mess things up before they notice what they're doing. On the other hand, buying two different blocks would have been more expensive.
Excellent value, top quality, highly recommended!