I ordered a size 8, which is normally only slightly large on me and which I like because then I can add a heavy sock with no issues.  My foot width is a little wider than a Medium (B) and a little smaller than a (W) wide width.  I purchased 2 inserts for these boots - one with arch support and one with a metatarsal pad. It's nice that the foot pad that comes in the boots is removable; I added both of my inserts, then replaced the original foot pad and the boots fit perfectly.  I absolutely love them.  I've been wearing them around inside the house for a couple of days, at 68 degrees,  and they are comfortably warm to me, even with a medium-heavy sock.