Although not yet tested in extreme cold conditions I was extremely impressed by the quality of this set and when put to it's intended use in the cold, expect it to perform as good as it looks.
Ordered the mens XL/womens XXL for my partner,the top fits him perfectly (he's about a 42" chest size) although the bottoms are too long in the legs as he's only 5'6" tall. I tried it on (I'm a size 14/16 and 5' 8")and although the overall size was too big for me, the length of both the top and bottoms fitted me brilliantly (I'm 5' 8") the top coming down well over my bottom and the bottoms plenty long enough in the leg. I've now ordered a size down for myself, mens L/womens XL (I'm a size 14/16).
I think you'd go a long way to find such quality at this price.