I'm a petite framed woman living in SF and I was going to Boston, needed really warm under clothes. I bought the heavy duty line, the quality is awesome, very thick and comfy. I bought a XS top but it was too big so I gave it to my sister who is a small. I did buy a small in the pants and medium for my sister and that worked out great, though the waist band comes up to your belly. The heavy socks were great as slippers but they are so thick your shoes need to be a size larger! Would buy again!