I searched very long for a pair of boots that would be comfortable for me to wear all day long.  I am on my feet all day at work and have plantar fasciitis in one foot so comfort and support are key.  These boots fit the bill.
The calf was tight as first.  When the boots were first delivered I couldn't get them zipped up all the way.  I was heartbroken and really thought I might have to return them.  I persevered and tried again the next day after work, I really worked with them and finally got them zipped.  I wore them around the house for a week.  They do stretch!  I even called my local Clark's store and the sales clerk said I could bring them in to be stretched.  I never made it there and have successfully stretched them on my own.
I first I could only wear them with skirts and tights, but now they have streched them enough that I can wear them comfortably with skinny pants.  These boots are wonderful and worth the time and effort of breaking the calf in.  I have 15 inch calfs so not super skinny or large. Just average.