Does its job, but worth the purchase.
The magnets are strong and it will cling to any metal surface, but a fourth magnet would have definitely given it just a tad more power. Nevertheless, I have yet to stick anything heavy enough in it to make it fall or lose its grip.
I did notice that when it accidentally slides around it leaves black marks on my white metal filing cabinet. Unfortunately, I am not sure if that is due to the paint job on the cabinet or the quality of the magnets/rubber stoppers.