When we can't decide on a long-sleeve jersey or not, we simply pull on the Pro Seamless 2 Arm Warmer and get moving. This arm warmer from Castelli lets us control our temperature easily and transition between layers in seconds. It features the ideal balance between warmth and lightness and provides enough warmth to keep us moving through chilly days. When the sun decides to poke out from behind the clouds, we can easily stow away our arm warmer in our jersey pocket and carry on.