Crisp mornings, warm afternoons.
On days when you know you need something extra under your jersey, but you don't really want to feel an extra layer, grab Castelli's Pro Issue Sleeveless Base Layer. Constructed out of lightweight polyester 3D mesh, the top fits under a jersey and facilitates moisture transfer from your skin to your jersey to keep your temperature regulated on crisp fall days or cool spring mornings. The 3D mesh forms a thin insulating layer next to your skin to keep you warm, and as you heat up, the material will continue to wick away sweat to cool you off. On this year's version, Castelli widened the collar to fit better under aero jerseys and included a flat waist hem along the bottom to prevent chafing or irritation when tucking it into shorts.