When conditions are cold but we don't quite need a thick jacket, we pull on the Castelli Flight Air Long-Sleeve Jersey. Built with a close-to-body fit, this jersey doesn't sacrifice aerodynamics with its tightly woven Nano Flex Light fabric designed to block wind with a thin, compact construction. Combined with this wind-blocking material is Castelli's 3D Mesh fabric, built-in as a front lining to provide an extra layer of warmth and moisture management.