These shirts use a new type of technology to light and flash without bulbs or LEDs. Using ultrathin Electroluminescent technology and a sound activated sensor, the T-Qualizer shirt comes alive wherever you take it. Sound and music make the shirt jump with brilliant color - *adjustable knob on the driver to adjust to the level of sound/ music.All T-Qualizer Shirts are hand wash only 100% cotton. DO NOT MACHINE WASH. Keep the display dry. Powered by 4 AAA batteries, the small power pack is tucked away in a packet at the base of the shirt. The battery pack can be removed for easy cleaning.