Smartwool has updated the fit of the Womens Classic Thermal Merino Base Layer 1/4 Zip to improve functionality while also enhancing aesthetics. As one of their heaviest base layer tops and one of the best base layers for cold weather, this garment uses 100% responsibly sourced Merino wool, shoulder panels, and a flatlock seam construction to help prevent chafing as well as keep you comfortable and temperature regulated as you enjoy high-intensity skiing, hiking, running, and more.