It's difficult making arm warmers warmer. If we understand we'll be riding in conditions where a pair of arm warmers will not keep us sufficiently warm, we tend to choose a thermal jacket. But, exactly what if the day ends up being intermittently cold and damp? Well, the Castelli Nanoflex Arm Warmers are created for days that provide everything from cold and damp to sunny and dry. Nanoflex is a proprietary Castelli fabric. The mill begins with Castelli's super-warm and ultra-stretchy Thermoflex fabric, utilized in many of its winter pieces, and after that coats the outdoors with small nanofilaments of silicone fiber. These fibers create a near water-proof obstacle to wetness, and raindrops run the fabric without soaking through. Despite its water-resistant surface, Nanoflex fabric continues to be extremely breathable, keeping you comfortable in almost any conditions. Silicone arm grippers keep the arm warmers in place on the hardest rides, and reflective logo designs are printed at the elbow and lower arm to enhance your exposure to motorists in bad light conditions. The Castelli Nanoflex Arm Warmers are readily available in four sizes from Small to X-Large and in the colors Black, Red, and White. Please note that Castelli advises utilizing these warmers at temperatures ranging in between 50 and 60 degrees Fahrenheit.