I have worn Birkenstocks for years (about 13 years, to be exact), so I do know quite a bit about them.  I currently own the traditional Bostons (nubuck) and a pair of nubuck Arizonas.  I've also owned some from the Tatami line.  I was really excited when I found such a good deal on these "Bostons", and was really stoked when they came in the mail.  However, as soon as I went to try them on... instant disappointment.  I ordered the "Habana" (though I'm sure they all fit the same) in a 43 Regular, which is always my size.  The bottoms of them were the same length/width as my other Bostons, but these were SOOO small on top.  Granted, I do have somewhat of a wider foot with a high instep, but I've always worn 43R in Birkenstocks and have never had this problem.  They weren't just a little tight, either.  They were "can't get my foot in without spending 5 minutes shoving/pushing/inching it in".  Then once they were on, they were literally so tight my foot would instantly have marks all over it.  Maybe there's some variation in the size of the top, depending on the tanning process, since it is real leather.  However, if you have a wide/tall foot at all, I would not recommend you get these.  The leather is thick, stiff, and very "short" (there's not much space between the insole and the top of the shoe).  I tried cramming them on and wearing them for a few minutes at a time, but they had NO give and were very, very tight.  They are called the Boston "Braid" (according to the box), in case you were wondering.  They seem well-made, and look very nice... too bad they didn't even come close to fitting!