Ideally, our arm warmers should do it all- keep us warm, block wind and water, and fit like a glove. Oh, and they should be lightweight, compact for stowing away in a rear pocket, and stay in place no matter what we put them through. We do ask a lot, but fortunately Castelli not only listens and understands, but has the skills, materials, and cycling experience to not only meet, but exceed our demands. The Nano Flex+ Arm Warmer is just the latest example.

The advances in lighter weight, yet highly effective cycling protection accessories has been startling over the last few seasons. For Castelli, Thermoflex gave way to Nano Flex, and now Nano Flex+. The vaunted insulation, breathability, and stretch of Thermoflex has carried forward, with Castelli adding a thorough coating of nanofilaments, which impregnated the fiber to create a highly water resistant version called Nano Flex. The company then developed a lighter weight, slightly less insulated version, referred to as Nano Light. Nano Flex+ products combine main panels of Nano Flex with sub panels of Nano Light. The advantages come from the greater stretch of Nano Light, which moves more easily at limb joints such as knees and ankles, without compromising fit. So the rear anatomic panels on the Nano Flex+ Arm Warmers feature Nano Light, delivering better ergonomic movement while warmer stays in place better during pedaling action. Nano Light also breathes at a faster rate, releasing excess heat and moisture more quickly and still providing excellent protection from wet, sloppy conditions.

Castelli maintains all the key features from the Nano Flex version. You still get double sided silicone grippers at the upper arm, to best hold above the biceps The pair are left and right specific, with anatomic paneling to offer some mild compression and proper fit. You don't sacrifice any of the top-level water protection, and the standard Nano Flex panels provide considerable thermal regulation and support from 46-72° F. The better fit and cleaner ergonomics supplied the stretchier Nano Light panel deliver higher overall performance with a greater temperature range. At just 69 grams for a pair in size medium, they are lighter, and more compact when rolled up then the Nano Flex-only version. What truly separates the Nano Flex+ Arm Warmers from a pack of hungry competitors is the incredible water and wind blocking that serve to make this the most versatile and effective arm warmer on the market. if you live anywhere it rains, and you ride in all conditions, you need these arm warmers.