In Northern Nevada, we had a cold wave that came in and just stayed and stayed and stayed.
I work outside and needed to add another layer of warm insulation to my wardrobe and took a gamble on this union suit.

It helped a lot and did the job in comfort.
The only drawback may be forcing you to think ahead of schedule for any bathroom episodes, as this does add time to the stages necessary to complete the human endevour.

They seem to be well constructed and they do keep you warm when combined with other winter cloths.
They get too warm when we get back up to the mid thirties, but feel good down to and including below 0.