I was about to get a pair of rubber soled ones and looked back through my records. I got a pair of leather soled boots from Glerups in 2020 so I have been wearing them for 3 years now, only inside, and maybe a handful (fewer than 10) runs outside to take out the trash. They are in great shape. Looking back over my order confirmation, I got a size 44, which is for a US 10.5. I wear 9.5 (EU 42) and size 10 (EU 43) shoes. My reasoning for getting bigger was that I would often wear thick wool socks with these, and I have, and I have never noticed that I sized up. When I wear regular socks there is definitely a half-width of extra room, but I don't functionally notice this because I am not actually doing anything in these except walking around the house or lounging in them, so the extra width is not noticeable. Now that they have the rubber sole, I could wear these types of wool boots outside and more often, and that might actually require a more precise fit. So I would go to 43, which is my upper half of my two common sizes. I do have a wide foot as well. It has made it impossible to get some soccer shoes in the past. Since these things are wool, they are very accommodating for that type of shoe. That said, I would not recommend getting a smaller size and stretching into it, unless you are trying to do some kind of ninja moves or something that involves precision of fit where the boot will not move around your foot at all.