This is so incredibly thin I figured it would not keep me warm AT ALL, but it at least does an ok job at that. I would not say that it makes me nice and toasty on a cold day out skiing, but keeps me from being completely chilled to the bones. However, unlike every other "long underwear" I have ever had for skiing, this is not long in length at all. In fact, I can only wear it with ski pants as they come up higher than normal pants. Jeans don't even reach the bottom of this top, just leaving it hanging open on my midriff which is a very poor design. I don't see anyone else mentioning this so maybe I just got a top form a bad lot, but I thought it worth mentioning. The top is good for one of many layers, but I can't really count on it as a sole under layer to a sweater and coat as it just doesn't do THAT great a job at keeping you warm if you are out in the snow. If it is just mildy chilly and you are wearing them to add just a thin (and I do mean thin) layer for extra warmth then these are for you