Smartwool Women's Classic Thermal Merino Base Layer 1/4 ZipWe've updated the fit of our Women's Classic Thermal Merino Base Layer 1 4 Zip to improve functionality while also enhancing aesthetics. As one of our heaviest base layer tops and one of our 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,