I don't know if we're now measuring calves in a way that flatters people (silently subtracting 1-2 inches), but this is def. not the circumference advertised. Closer to 15"+ for sure. I am 13.5" and I wore these with thick leggings and they practically slip right off.  When I adjust the top strappy thing to the smallest size, it fits better, but, two undesirable things happen: (1) the top is now pinched/cinched in, but the boot then triangles out along the sides, because the *whole* shaft is too wide and the inset is too short; (2) the strappy itself dangles out like funny wings. I am thinking of cutting them.

The heel also slips, so if I don't wear super thick socks I end up with blisters on my heels.

I will say that what I really like about this boot is the sole--very traction friendly.