If there’s one failing of most warmers it’s that they absorb water like a sponge. On rainy days they end up waterlogged and providing compromised warmth. Nanoflex is a proprietary Castelli fabric. A super-warm and ultra-stretchy Thermoflex fabric, used in many of Castelli's winter garments, and then coated outside with ultra-tiny nanofilaments that cause raindrops to run off the fabric without soaking through. Despite its water-resistant finish, Nanoflex fabric remains highly breathable, keeping you comfortable in almost any conditions.
Exclusively engineered by Castelli, NanoFlex consists of Thermoflex fabric with millions of tiny silicone nanofilaments on the surface to create the most water-repellent finish ever. In wet conditions, water droplets simply bounce off the fabric without leaving a trace. The silicone nanofilaments also trap a layer of air between them for excellent insulation and prevent water from soaking through to the fabric underneath. In dry conditions, Nanoflex provides the same warmth and feel of the regular thermoflex fabric. NanoFlex is not completely waterproof but maintains full stretch, breathability and freedom of movement for weatherproof protection with un-compromised performance in all conditions.