Wendy -
I'm not sure if it's meant as a nipple "ring" per se, but rather as a round-ish type disk that is "pasted" over the areola/nipple area. A stereotypical version are the kind imagined in peep-show situations wherein the pastie has a dangling tassle extending from it.
The only legitimate reason I can imagine for wearing one is if a women expected to expose a very lacy bra that might reveal too much through the lace. A pastie could conceal some of that.
All in all, something that I imagine most of us normal gals would just want to steer clear of!
Lynn
