I bought a red union suit for warmth to sleep in on cold Maine winter nights, and it is warm as anticipated. The suit has a droopy butt, but no one will see it :)
I expected shrinkage (100% cotton), but was dismayed by the fabric twisting markedly when washed. Less comfortable with twisted legs.
I have always had a problem with the shirts on two piece long underwear riding up and leaving my back cold, especially when I lean forward or curl up. This kept me warm on my last camping trip and did everything it was supposed to do. The button holes are not finished like in most garments and have stretched out after about 10 wears.
about 25 + years ago, I bought a shirt and a nightshirt, men's small, blue.
I am still using both. but they are wearing thin. I would like very much to replace the night shirt which you no longer seem to carry. So I bought the union suit.
it does not have enough fabric for me to convert it to a dress and I am forced to use it as is. I have crushed my fingers several times while trying to hold the flap open and sit. It is far too awkward to remove the whole suit for a minute of need.
I also bought the shirt (men's) last fall and love it, but it is not long enough to be a night shirt.