The Polartec® Alpha® fabric is an amazing insulator, and it's soft, stretchy, and lightweight. A couple of years ago we thought it would make an excellent fabric for a base layer, but it tended to feel wet and clammy against the skin. But when looking for more insulation for sub-freezing gravel rides, we tried using the Alpha prototypes as a second layer on top of a Prosecco base layer — and stumbled into the best combination for cold riding. We worked on the details and created this second layer for cold rides. We've given it a half zip so it doesn't create bulk over the lower torso, and we've mounted the zip slightly off-center to avoid the bulk of multiple zippers at the neck. We've kept the fit close to body so you have the choice to tuck it into your tights or leave it out like we do. We also found that it works well over a Flanders, Bandito, or Miracolo base layer.