Keep your heart rate up when the mercury drops. Fleeced fabric holds the heat in when winds pick up or temperatures plummet, but is breathable enough for interval training. Silicone waist prevents jersey from riding up, while the dropped rear hem protects against wheel spray. Polyester Castelli Warmer thermal fabric holds in the heat. Warmer X-Stretch fabric on sleeves and side panel provides a dialed fit for when layering with a vest or jacket. Full-length YKK Vislon zipper provides added ventilation when digging really deep. Silicone waist gripper. 3 rear drop-in pockets for no-nonsense hauling. Castelli recommends use from 13 to 20°C.