I bought X-Large and you you think they would have enough room in seat to be comfortable but no they don't. Feels like they are being pulled down. there is no elastic in the waist to help. I wear x large in other brands fine so I won't be buying these again. The legs do stay warm in 45 degree weather.
I liked the quality of the product. Unfortunately I couldn't even fit my foot and ankle through these tights. Extra small wouldn't begin to describe the actual size ( it was labeled small). Not sure whether this was specific to the pair I received or it is a general issue with these.