I love these boots but I didn't realize they did not have a zipper. they have two stretch gores on either side but I have a high instep and my left foot is half size larger than my right. I managed with some difficulty to get the right one on and it was very comfortable but I simply could not get the left one on over my instep so I had to return them I purchased an 11 and I am a 10 on right and 10.5 on left foot. There was plenty of room on the right foot so if I could have gotten them on the left they would have been fine. I would say they run true to size.