They are~ Not that commonly for most, but it's certainly a thing that's done.

[Considering the circles she ran in, it's not terribly surprising that she would have come across something like this at some point or another. Though the toying and gentle tugs doesn't seem to bother her in the slightest, in fact it seems to be getting those poor nipples hard fairly quickly and she's doing her best to keep an iron grip on the silks to make sure she doesn't fall. It's a lot of work, but she doesn't mind the work-out.]

Both~ [Shit, it has been a while since she'd had these in and she can't help the shudder and bitten back groan, it's super nice for her.]

In fact you can tug if you want. Just don't rip and you'll be perfectly fine, I do quite enjoy the pain of it, darling~