The Finis Thermal Training Shirt has a dual purpose of providing warmth to swimmers by trapping body heat with its unique Nobel prize winning Polyolefin fabric, and elevating training with the natural resistance provided by the shirt. Made from strong, yet lightweight material, the Thermal Shirt conforms to a swimmer's torso but does not restrict range of motion. Elevate endurance and increase muscle while wearing the Thermal Training Shirt, then remove it for higher speeds, recreating race pace. Stay warm with this Nobel prize winning Polyolefin fabric Light weight fabric does not absorb water or add extra weight Conforms to the body to provide a full range of motion Machine washable