In rainy conditions, knee warmers suffer from the same problems that legwarmers do. Basically, the fabric absorbs water and their ability to keep your joints warm becomes compromised. Lucky for you, the Castelli Nanoflex Knee Warmers have remedied the issues that challenge knee warmers in cold and wet conditions. Nanoflex is a proprietary Castelli fabric. The mill begins with Castelli's super warm and ultra stretchy Thermoflex fabric used in many of its winter pieces receiving an exterior coating of ultra tiny nanofilaments of silicone fiber. These fibers create a near waterproof barrier to moisture, and raindrops run off the fabric without soaking through. Despite its water resistant finish, Nanoflex fabric remains highly breathable, keeping you comfortable in almost any condition. Silicone leg grippers keep the knee warmers in place on the hardest rides. But, keep in mind that they do run longer than some that we've seen more accurately, they run from mid thigh to the bottom of the calf. Lastly, Castelli printed reflective logos at the knee and on the side of the calf in order to increase your visibility to motorists in low light conditions. The Castelli Nanoflex Knee Warmers are available in four sizes from Small to X Large and in the colors Black, Red, and White. Please note that Castelli recommends wearing these warmers in temperatures ranging between 50 and 60 degrees Fahrenheit.