Product review (3 stars): package was opened, but works fine
Received the package, and found there was a tear on the plastic bag. The sticker which was supposed to seal the filter was partly open, and there was something black stuck on it.

Contacted seller, and seller replied saying:

1. No one tampered your filter
2. The sticker is OK
3. The black stuff is carbon, which is used in the filter

I believe the 3rd point, and I really don't have much time for a return / replacement, so I just screwed it on and started using. It works fine so far - see, if there's something wrong about the filter, I won't survive this long to write this review :)