The Core Seamless Long Sleeve Base Layer is fully seamless, so you can wear it in comfort, even under race-fit, aero jerseys. Made from a mixture of polyester and polypropylene, it will stretch to allow you full freedom of movement as you ride.It's also warm and soft, as well as highly wicking, so you won't get chilly in the easy stretches of your ride, not overheat on the intense ones, and when you stop for a break you'll be dry and your temperature will remain stable.Overheating is further deterred by lightweight sections at the sides and the back of this base layer, to ensure that you'll enjoy consistent insulation across your upper body, even in the areas where your bib shorts, base layer and jersey overlap. Finally, a wide neck will sit easily under short-collared jerseys.Features:84% polyester/16% polypropylene yarnsSeamless construction means extra comfortLighter weight on side and backWide neck opening to fit under short-collared jerseysWeighs 194g (L)Castelli comfort rating of 4-16°C