I'm trying this tutorial from Line25. So, after downloading the icons I must select four of them in order to build this menu:

But, according to CSS, the size of each square is 120 x 120 px. And this is what I achieve putting an icon into a 120px square:

Quite smaller than the original. The author of the tutorial did not use Illustrator to assemble the four icons but Photoshop, so he couldn't enlarge them.

What did I wrong? Thanks in advance.