The only no-show socks I have found that don't show AT ALL under ballet flats.  As socks go, these are made out of a thin material (a little thicker than thick tights) - which is good if you want to wear them under shoes that fit you barefoot, since the socks won't make the shoes much tighter.  They mostly stay in place - I might have to adjust once or twice during the day - and they are comfortable and don't leave any marks on my feet.  Wearing them keeps my feet feeling dry on hot days and prevents my shoes from getting stinky.  Very happy I bought these!  Also, there was a promotion when I bought these to get a free lingerie bag, and it's the nicest lingerie bag I've ever owned!