Extra durable SA M05 merino wool liner sock has multilayer sole. Sock is very breathable and absorbs moisture. Merino wool is warming and breathable which makes it best material for year round use. Merino wool is antibacterial and dries quickly with ventilating. Ribbing on the shaft keeps sock well on place.Every size has different amount of stripes on the shaft to make easier to find right size pair! Smallest size has no stripes.