Building on our protective Winter LS Skin Layer, the Ultraz edition turns up the warmth and windblocking capabilities even further with its wool-blended knit. We see this as the ultimate defensive first layer in the most challenging winter conditions, as it goes into overdrive at the core level to keep you dry and your temperature stable. Setting a new foundation, Skin Layer is a total reset on our base layers of yore, wearing a completely revamped, lighter makeup and using a new blend of fibers. This Ultraz model is about 10% lighter than the previous Winter LS Skinfoil, relying on a Circular Seamless construction that's both ultrasoft and free of irritating side seams. A robust arctic-tuned blend of polypropylene and wool are also employed, serving as the ultimate next-to-skin foundation when maximum thermal- and windblocking-protection are most critical.