Castelli NanoFlex 3G Cycling Arm Warmers - Black. Nano Flex all-condition warmers. Choose Nano Flex for warmers that are great in dry conditions but also give some extra protection and warmth in wet conditions. We invented the category of water-protective thermal fabrics, and Castelli's proprietary Nano Flex is often imitated but never equaled. No compromises for any conditions. Features: Water-repellent thermal and breathable Nano Flex fabric, Flat-lock stitching with single seam, Double-sided silicone grippers to keep warmers in place. Weight: 66g. Nano Flex for the ultimate warmer: warm and comfortable in dry conditions, water repellent in damp conditions, and still warm in extreme conditions. Key Features: Water-repellent thermal and breathable Nano Flex fabric, Flat-lock stitching with single seam, Double-sided silicone grippers to keep warmers in place. Warm fleece inside. Very breathable and fast drying fabric. Improves UV protection.