Smartwool took their popular Merino 150 Base Layer and added a 1/4 zip to it. This Smartwool base layer is amazingly versatile and perfect for unpredictable weather—working as a single layer when it's warm out and the perfect start for more layers when the sun begins to hide behind the clouds. With Raglan sleeves and a flatlock seam construction designed to minimize chafing, you'll be able to rely on constant comfort all day long.