If you take your baselayer game seriously (and you should), the Smartwool Intraknit Merino 250 Thermal 1/4 Zip Baselayer Top is the holographic legendary version. 100% pure Merino wool is incredibly insulating, breathable and odor-resistant, with a combination of 3D mapped zones and mesh ventilation panels for a premium baselayer that is durable, free-flowing and comfortable.