Smartwool Classic Thermal Pattern 1/4 Zip is here to bring you a better feeling, better performing, and better-looking garment. As one of our heaviest base layer tops and best base layers for cold weather, this garment uses 100% responsibly sourced Merino wool, shoulder panels, and a flat-lock seam construction to help minimize chafing as well as keep you comfortable and temperature regulated as you enjoy high-intensity cross country skiing, hiking, running, and more.