I don't like to think about what they're made of at all but Muffin LIVES for Flossies!! She can't get enough of them. Biscuit can take them or leave them. One nice thing about Muffin chewing on these all the time is that she never chews on anything she shouldn't and her teeth are almost tartar free too.
I think the flossies don't leave that horrendous breath smell like the bully sticks do. Muffin's breath never smells bad after chewing a flossie but when I've given her bully sticks I want to gag because her breath smells like a sewer.