The new 8-oz. material increases wicking keeping you dryer and more comfortable. NRS HydroSilk is the perfect solo layer when the weather gets warm and makes a great base layer when it's cold. The fabric has a sun protection factor (UPF) of 50. The new 8-oz. nylon/spandex fabric improves moisture wicking to keep you more comfortable. Fits snug for easy layering.UV protection-factor of 50 guards your skin from the sunÆs harmful rays. A silky outside and soft-brushed inner feels great against the skin.