Smartwool Womens Merino 150 Blue Striped Short Sleeve Base Layer Shirt Size XS. Smartwool womens Merino 150 base layer shirt. Round neck. Short sleeves. Merino wool and nylon fabric blend. Blue and white stripes. Logo on left side hem. Size XS. Measured laying flat: 16.5 inches from pit to pit, 24 inches long from top to hem. Basic, staple, base layer, active, warm, ski, snow