Castelli Nano Flex Plus Knee Warmer

When the forecast is slightly chilly with a chance of drizzle, be proactive about your knee protection with a pair of Castelli's Nano Flex Knee Warmers. They'll resist the elements so your tendons stay dry and happy to turn over long, cloud covered miles. Nano Flex starts its life as the warm, stretchy Thermoflex fabric used in many of Castelli's winter pieces. It then gains an outer coating of tiny nanofilaments of silicone fiber that create a water repellent barrier so raindrops and road spray dead up and run off without soaking through. Despite its water resistant finish, Nano Flex fabric remains highly breathable, keeping you comfortable even when rain falls in the low 60s. Across the back, Castelli uses a panel of its lighter Nano Light fabric to increase stretchiness behind your knee for full freedom of motion without reducing protection from the elements. In our experience, the previous generation of Nano Flex warmers tend to bunch behind the knee. This is a common ailment in knee warmers, so it's a small price to play for dry joints, but the addition of Nano Light helps to address that common nuisance. Silicone grippers on both faces of the thigh hem and the inner face of the calf hem keep the warmers in place.