This is the piece Castelli pros requested for those in-between conditions where the Prosecco base layer is too warm and the Core Mesh isn't quite enough, like Spain in February or Belgium in April. You’re not looking for warmth from your base layer, just something to move the moisture away from your body and help your race jersey perform. Castelli's 3D mesh fabric creates dead air space next to your skin, while the polyester capillary action moves sweat away.