I have metal plates in my ankles, which makes them a little bit thicker ... I am 5'7" and I weigh 143. I ordered a size big because I always worry that they're not gonna be big enough to comfortably go around my ankles and not push on the screws and plates. I have a blade type prosthetic device on my other leg and these stretch around it just fine. The last pair, ovation, I ordered were for much more narrow ankles, and the way the leather was stitched, pushed right on one of my screws and caused me discomfort. I was really pleased with the roominess of these boots. If you have skinny ankles and narrow feet, probably not for you unless you're planning on wearing layers of thick socks… I can attest to the waterproof of these.... they absolutely keep my feet dry and decently warm.
Are they going to keep your feet warm in below 30°, probably not, you probably ought to wear some thick socks in that case, but, it is 35 to 45 here regularly during the winter and I am having no issues keeping my nerve damaged foot warm enough. One thing, though… The tread absolutely grabs mud and grass and stuff like that and packs it up in there, so be aware that once you wear these outside in the mud, you won't be wearing them inside anymore...... these are super lightweight though!! Freaking awesome!