They are not bad socks, but if your feet are muscular or if you are overweight, these socks are NOT SUITABLE for you unless you turn them inside out, so they reach about halfway up your calf. As for thermal insulation, I haven't formed an opinion yet, but I think they are as effective as a pair with at least 50% wool. In contrast to wool ones, the feeling on the skin is like day and night. They are so soft that if you wear wool ones afterwards, you will think you put on a burlap sack... Finally, the quality of construction seems decent. If something goes wrong over time, I will come back with an update...