 That means that I'll be putting multiple layers of wool socks in. I'll have shearling liners that I add to my shoes. Most running shoes are going to have a mesh so that they're breathable. That's something that I have to try to avoid because anything that lets air out can also let snow in. So it's that trying to trap as much heat in as you can but needing a certain degree of breathability because you're still working. Your feet are still sweating. And sweat, like I said earlier, it's a freezing process.