Sorel Caribou can handle really cold winter days. It is warm, comfortable and waterproof and it has a warm ThermoPlus inner lining that is removable. there is a 2.5 mm frost plug in the midsole to prevent the cold from penetrating the ground. The outsole is equipped with friction studs to minimize the risk of slipping. Think about how you dress underneath; we recommend a functional or wool sock for the best warmth. When you have used the shoes, we recommend that you remove the inner shoe and set it to dry, in this way you protect the shoe against wear and you will also keep the heat better when the inner shoe is properly dry. Size guide (inner dimensions):US1 / EU32 = 19 cmUS2 / EU33 = 20 cmUS3 / EU34 = 21 cmUS4 / EU35 = 22 cmUS4.5 / EU36 = 22.5US5 / EU37 = 23 cmUS6 / EU38 = 24 cmUS7 / EU39 = 25 cm Note that this is the inside measurement of the shoes. If you add 1.5cm, you get the recommended foot length.