Even different shoes within a brand or the "same" shoe with an updated design can fit differently. I wear a size 8 street shoe. My old Weinbrenner boots are a size 8 and I have plenty of room in the boot. I have some 10 year old Simms Freestone boots that are also a size 8. However when I got a pair of new Freestone boots last fall I had to get a size 9.