I don't know about the site itself, but from the pictures, it looks like you are buying a legit 360S hdd. Granted I have never seen a 360S hdd other than pictures, but this does look legit.
I would just check around the site to check for a return policy and if there are any safeguards in place in case if you never get your item, I would also check Better Business Bureau and see if they have anything to say about this site.
Other than that, I don't know what to tell you.
Edit: Didn't realize this was a HK site, guess BBB won't get you anything...in that case, Good Luck.
After looking a little more at the site, I think I would give them a shot, seems like they will work with you if something goes unexpectedly.