Guess what's being advertised

[kirisutogomen]

If you read Chinese, don't spoil it for everyone else, although do comment about how much harder it is to read after I performed a simple alteration whose nature is obvious to you but may not be to non-Han-character-readers. If you can't read Chinese, guess what is being advertised in this image, and I'd be curious to know how obvious the nature of the alteration is to you.

Comments

[dcltdw]

Now that greyautumnrain points it out, it does look mirror-reversed.

I'd guess phone cards.