Their popular Classic All-Season Merino Base Layer 1/4 Zip is the perfect base layer for warm or cold weather. This top uses their All-Season-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. This base layer is comfortable, powerful, sustainable, and, frankly, do-it-all-able.