Leave black marks - not recommended

Before I ordered these magnets, I've looked at some reviews here, and read again and again that these magnets rub well and leave black marks. Since this but actually a good brand, I wanted to not quite believe it and thought maybe it would be in other circumstances.

So I ordered it and tried. And what? In fact, they left black marks! And not just weak!

Attach directly at first saw the paper from underneath dirty. In the menu from the Italians, the one attaches itself to the whiteboard, which is perhaps not so bad - but with personal cards or invitations I find it really annoying!

Have the magnets therefore packed and sent back directly again. Absolutely not recommended.