Smartwool has perfected the baselayer, and the Intraknit Thermal may be the creme of the crop. Thanks to this being made with IntraKnit you will feel ideal insulation, full mobility, and breathable ventilation all at once. It is slim fitting so it wont take up any space either. Made from a merino polyester blend for optimal performance and warmth. 3D mapping in specific areas of the top to provide ideal movement. Plus, the colors look pretty great.