The Castelli Nano Flex 3G Arm Warmers provide a waterproof and windproof layer to keep your arms warm during rides. They feature Castelli’s Thermoflex lining with a fleece-like inner that traps warm air against your skin, ensuring warmth on cold days. The Nano Flex stretch outer offers an aerodynamic fit and repels water, keeping you efficient and dry. Perfect for cold or wet mornings, these arm warmers help you enjoy your ride regardless of the weather.