Our lightest weight Merino jersey fabric uses a nylon core to increase durability while still keeping 100% Merino wool next to skin Offset shoulder and side seams designed to increase comfort and minimize chafing while wearing a backpack Side seams wrap to front for body-enhancing fit Flatlock seam construction designed to minimize chafing UPF 20+ Black Marble Wash, Light Woodsmoke and Indigo Blue colorways feature plant-based dye technique