Protect your knees from the cold on descents and chilly morning rides. A set of knee warmers adds versatility to your bib short and are great for spring and autumn climates. Nano flex is highly water resistant and thermal, giving you premium protection. Top Features of the Castelli Nanoflex Water Resistant Knee Warmers Water-resistant nanoflex fabric Same breathability, stretch and warmth as Castelli standard thermoflex warmers Great in all conditions Product Data Road: Yes Castelli don't claim that it's fully waterproof, but it's the most effective thing they've ever made for keeping you comfortable in all conditions. It's just barely short of a miracle.