"The Patagonia R1 Air Zip Neck Top is the layer that earns its place between skin and shell on days when the effort level stays high. The hollow-core yarns and half-zip work together to keep temperature manageable without stopping to shed a layer. What Our Gearhead® Experts Are Saying:""I wear this as my first layer on high-output ski days because the hollow-core yarns move heat away fast enough that I'm not stopping to unzip every run. The half-zip handles the rest when I need a quick vent."""