First, I LOVE the Naughty Monkey Detective boot which is no longer out there.  I bought this boot in gray and do love it, but agree with other reviews I've read.  The opening at the top is quite a bit smaller than the Detective Boot - probably about 1.5 inches smaller (I believe Detective was 15in).  There is also less "shrug" in the boot.  I still love it and will keep it, but be warned that if you have bigger calves, this may be a bit more snug on you.

Great quality and the gray color is just what I was looking for.  Also note, these only come to mid-calf... the picture can be deceiving and make them look higher.  I've also seen them listed as knee high boots on other sites.