A cycling base layer is a vital part of your cycling wardrobe that can be used in all seasons. A base layer designed for winter will have thermal properties to ensure you keep warm while also transporting moisture away from your body, summer versions will be slightly lighter without thermal protection ensuring you don't overheat on hot days.The design and fit is based on a compression fit resulting in a close to body style and in some cases, they will be specially designed for cyclists by providing slightly longer sleeves including a tail at the back for additional protection.