The Sasha short sleeve schooling shirt is made with 37.5® technology. The patented thermoregulation technology has proven to help your body manage its core temperature and therefore, increase stamina. It keeps you comfortable by helping your body to maintain an optimum core temperature of 37.5° Celsius (99.5° Fahrenheit) which is ideal for peak athletic performance. The particles are naturally derived and work for the life of the product (it will never wash out!).