The Castelli Viva Thermo headband is thin but warm thanks to Thermoflex fabric. It helps to cover the ears and easily fits under a helmet. Remember headbands allow for heat to escape from the top of your head, something caps will not due. This will cut down on unnecessary perspiration which is the kiss of death on colder rides. The Viva is perfect for those who like warmth without the bulk and considered by many cyclists as the best 3 season headband.