I used the Radiant Tight last spring on a trip to Alaska. These went under my ski pants on really cold days. They work great as a base layer on bone-chilling ski days and are great to use for running/yoga down day activities or winter camping. They do run a bit baggy, which can make it hard to have the perfect fit under a ski pant, but sometimes the loose fit is preferable. In the end, they are a really warm and versatile layer. I would definitely recommend having them in the quiver of fall/winter active clothes.