We took our popular Merino 150 Base layer and added a 1/4 zip to it—making it the perfect base layer for warm or cold weather. This top uses our lightest-weight Merino fabric wrapped around a nylon core to increase durability, while still keeping the 100% soft, Merino wool you love next to skin. Side seams help minimize chafing while wearing a pack and offer a body-enhancing fit. Select colorways feature a more responsible plant based dye technique. This base layer is comfortable, powerful, sustainable, and, frankly, do-it-all-able.