The Castelli Tech Long Sleeve Base Layer adds a second layer for cool weather riding. The long-sleeved base layer not only provides extra warmth, but warm air can circulate and evaporate sweat and excess body heat through the second layer. A hydrophilic treatment increases the already wicking capacity of the polyester and the PrimaLoft panels at waist and back are a synthetic microfiber insulator that adds extra warmth. These features ensure the body is equally insulated and kept dry. Crew neck is flat, and it fits comfortably under a short-collar jersey. The Tech Long Sleeve Base Layer is a comfortable and nearly unnoticeable base layer worn under your cycling jersey or jacket on cool days.