We took our popular Merino 150 Base Layer and added a 1/4 zip to it. This SmartwoolA;A(R) base layer is amazingly versatile and perfect for unpredictable weathera; "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.