Introducing the Smartwool Men's Intraknit Thermal Merino Base Layer 1/4 Zip. This Smartwool base layer is 3D-mapped for a near-custom fit and freedom of movement. Its engineered construction helps enhance your performance with a lighter weight and cleaner finish. If you're looking for base layer clothing for cold weather, this one uses Merino Sport yarn that combines the power and benefits of Merino wool with the durability and fast dry times of polyester- creating the ultimate performance-ready top for all of your high-energy activities. FeaturesFit: SlimSlim fit is intended to follow the contours of the bodyFeaturing Intraknit technology: Insulation, articulation, and ventilation are seamlessly integrated to help with movement and comfortMerino Sport yarn combines the moisture management, temperature regulation, and odor resistance of Merino with polyesterSeamlessly knit mesh ventilation3D mapping results in near custom fit and freedom of movement25" (21 cm) center-front zipper