This is the superhero of base layer bottoms. This stretchy knit fabric is soft and flexible and lined with plus merino so you've got that wooly goodness next to your skin. Plus there is a layer of durable synthetic fabric to battle the elements if you are wearing these somewhere other than skiing and riding. That is why we love it so much. It fits more like a yoga pant legging than a baselayer and has a drawstring waist...AND POCKETS!