is it accessory or cover?

[eReS]

what are those blacks on the corners shown on Nokia FB page?

 

[takisrock]

that shells designed for extra protection are normally pretty chunky and ugly,
these are the same width and same length as the other shells, and only a fraction thicker.

Poll: Your favourite Nokia Lumia 820 shells – Nokia Conversations : the official Nokia blog

 

[eReS]

thanks for the answer
I wasn't aware that they have extra protection shells.

[EDIT]
cc-3040
already available in Poland