They fit over my frames (which are the max size listed for this particular product). There's no real way to flex the frame to fit better, and the bottom edge of the frames is just hard plastic so I sometimes have to adjust them on my face because the plastic starts cutting in. For the price, and outcome I would buy again.

FWIW, though the fit was as expected they do "look" much larger than I expected given the "slim" part of the name but this isn't a big deal for me as I have a pretty large head (size 7.5-8 hat)