It did keep me warm under the snow pants that I wore over the base layer. The temperature was -45degrees C and the next day it went down between 5-15 degrees C. Both times, I felt warm.
The customer service for WoolX was phenomenal.
I also purchased the matching top but I couldn't write a review for the top since I placed another order with the top. The top also kept me warm as all I wore was a tee shirt, then the Woolx top and an outer coat. I was warm. Thanks Woolx.