My sister does it.. I don't know the size, but they look pretty fucking cool. She's an Anthro Major, and thus its more cultural to her than "trendy" On the plus side, you pay like 50 cents for a set of earings, just by going to the local hardware store. How cool is that?
Her favorite pair has an 'inside' that is clear with a skull in the center. Anthro Major.. skull.. Anthro, SKull? Yeah. It looks pretty cool though. Her boyfriend does it as well, fits him too. As for me? I just don't think I'd look right with them.