sizing a little bigger

I was excited to get another pair of Crispi boots as my two others, altitude and guide are are each a couple years old and in the need for a new pair. I went with this boot over the two previous models to give it a try. Out of the box very comfortable and no break in as normal. They did seem a little roomier than the others. I wear 11.5 and this seemed more like a 12. I took them on a sheep hunt and due to the more room, I got heal slip and ended up w/blisters in the heel. So since they were used, I had to pass them to my son, who wears a 12. He has had no issues with the size. If ordering this boot I suggest going down a half size.