Helly Hansen's Phantom Half Zip Turtle baselayer top combines supersoft merino wool and hollow T3 polypropylene for ultimate warmth and legendary LIFA moisture management. This winning combination takes advantage of wool's skillful temperature regulation and polypropylene's speedy moisture movement to create an extremely effective lofted midlayer. The loft holds warm air close to your skin, without trapping unnecessary heat when you're working hard in low temperatures. On cold winter runs, this top is all you need to keep warm and dry, and as a baselayer it stands up to freezing stop-and-go activities without ever feeling clammy, stuffy, or itchy. In the spring, head out to ski soft turns with just the Warm Freeze and a softshell to stay warm without overheating under a strong April sun.