Good thing it was my "backup". For some reason, a few weeks after buying the file, the abrasive parts had mostly rubbed off and the surface became smooth and "glassier". I went back to the store to get a replacement and they let me keep both, but I had originally expectes to be able to keep my crystal file for a lifetime (or at least a year!)
The replacement has been fine so far but I haven't used it too much. Maybe it will have the same problem...:/
I don't know what brand these files were otherwise I'd advise all you ladies to stay away from it. If I remember correctly I paid a few dollars (6?) for this, but it could've been on sale.