I actually saved the plastic film the block comes in, since I plan on popping it into my bag, and I don't want random things wearing the block down faster than it should.
The grey side for smoothing ridges... I wouldn't even have known that it was "rough" if I hadn't applied it to my nail! It is such a fine grit, and I don't know how it would have performed if I hadn't used the TRIM block prior to it, but I loved the performance anyway. As for the white, buffing side... don't get me started! Buffing with this block is almost effortless...
Another pic of the difference, TRIM on the left, EzFlow on the right:
I love this buffing block so much that I might buy a couple more, for just-in-cases! Already, my mother's resistant fingers have snagged on the smooth white buffer surface, and I'm afraid it will happen again. It's not the block's fault though, my mother was like "meh!" and not really letting me manipulate her hand -.-