iSkin DuoBand for Nano (Artic Flex) DuoBand - Artic Flex (includes clear silicone inner case, hard plastic outer case and black band) The DuoBand features a reflective strip to help keep you visible and safe. Durable polycarbonate outer impact-protecting layer Sweat resistant design Adjustable for a variety of arm sizes (8.5" - 19" / 21.6 cm - 48.3 cm)