...I have 15" calves and I couldn't get these zippered higher than the middle of my calf.  They are very narrow from the ankle up, so even if Keen claims the circumference is 15", that has to be at the very mouth of the opening, as if women have calf muscles that are nothing but a narrow band at the very top of their lower leg.  Like a hula hoop calf muscle.  Just plain weird.  Come on Keen, if you make the boot 15", you have to make it 15" in more than the just opening.  How about giving the upper 1/3 of the shaft a wider opening to match the shape of a calf muscle!  Oh, wait, you only thought you had to accommodate a pair of leggings, not a wider calf muscle.  If that' the case, then don't try to promote these for wide calves.  I love ya Keen, in fact, I have seven pairs of Keens and have hiked all of Europe in a single pair that are some of the best shoes I have ever owned, but you really should make a real effort to provide boots to women with larger calves.