SW016373 Smartwool Women's Merino 250 Baselayer Quarter Zip Smartwool has updated the fit of the Women's Merino 250 Base Layer Quarter Zip to improve functionality while also enhancing aesthetics. As one of SW's heaviest base layer tops and one of their best base layers for cold weather, this garment uses 100% responsibly sourced Merino wool, shoulder panels, and a flatlock seam construction to help minimize chafing as well as keep you comfortable and temperature regulated as you enjoy high-intensity skiing, hiking, running, and more.