Polartec® Alpha® fabric is an incredible insulator, and it's soft, stretchy, and lightweight. A few years ago, we thought it would make a great base layer, but it tended to feel damp and clammy against the skin. However, while searching for more insulation for sub-zero gravel rides, we tried using Alpha® prototypes as a mid-layer over a Prosecco base layer and discovered the best combination for cold-weather cycling. We worked on the details and created this mid-layer specifically for cold-weather cycling. We gave it a half-zip so it doesn't feel bulky on the lower torso, and we positioned the main zipper slightly off-center to avoid the discomfort of multiple zippers around the neck. We kept the fit close to the body so you can choose to tuck it in or leave it untucked, like we do. We also found that it offered good performance over a Flanders, Bandito, Miracolo, or Seamless base layer.