Hmm.. one is that way and one is not, though. And the one that is, seems to sustain more damage than the other. Like, after removing the clamps (clothespins), the uninverted nub is flattened, but returns to normal shape quite easily. The inverted one, however, is bent out of shape pretty bad, since the flesh puckered around the hole is far more easily bent. There doesn't appear to be any permanent effects or any more pain than usual, however, except perhaps the 'hole' in the middle appears to get deeper. Perhaps I really need to stop playing with that nipple?