Castelli opted to break out their warmer line into simple thermal and protective options. The Nanoflex 3G offers light thermal fabric that is water-repellent and blocks enough incoming air to keep you comfortable, but also carries thermal properties to keep you warm and dry at cooler temps. Castelli invented the category of water-protective thermal fabrics, and their proprietary Nanoflex is often imitated but never equaled.

The highly breathable Nanoflex fabric is relatively light weight and flexible. Castelli uses a single seam construction, with flatlock stitching on the seam and cuffs. The fabric offers plenty of stretch, but the design has also been aligned anatomically, with moderate compression. Double sided silicone grippers at the top hold against the skin and jersey material for excellent control. Castelli finishes the 3G Armwarmer with sleek, subtle embossed wordmark logos.