So far so good.  I had never thought about "earring sizing" before purchasing these, but they fit my apparently average earlobes just fine.  I wear them to sleep and in the shower, and so far, no problem with the backs loosening.  The backs are pretty tiny, so you don't feel them when you sleep (I am a side sleeper).  They are a nice size.  Small enough to pass for real.  I kept meaning to wear earrings, and then always forgot.  These are a great solution.  Nice looking and sparkly.  They come in a nice box too, if you are giving them for a gift.