Castelli nanoflex 2 bib knicker nanoflex really is at the cutting edge of fabric technology we go into the science in more detail below but the result is that nanoflex actively repels water where other garments let you down the nanoflex 2 is the answer when youre wondering what to wear in the rain just like castellis thermoflex fabric nanoflex is warm and breathable its extremely soft to the touch and traps a layer of warm air next to your skin its secret however is that its coated