This LED EL T-shirt is made of 100% cotton. It has an electro-luminescent panel (EL) across the front that reacts to music and and 'pump' in time with whatever you are listening to. It also gives a visual rhythm guide to others. It is powered by a battery pack that put within inside of T-shirt. And the EL panel canbe removed and replaced, its interface is universal, you can use the other EL panel to replace it. Stylish and convenient.