Just had someone install ceramic tiles for bathroom. But to my surprise one tile on the shower walls, appears to have a hairline crack. I asked him about it and he said it was a manufacturing cosmetic defect and it's not a real crack more like a harmless scratch. I don't know, but I know replacing it is not easy. The pipes out of the tiles are for the fauce, so there are two holes for them in the same tile already.
The tile has 4 horizontal squares and two vertical, the two important holes are in the center: