PREMIUM MATERIAL: This clear glossy mug is made of sturdy acrylic plastic, a material that is not harmful to the body. Just the right thickness, safe and comfortable to use. MAGICAL FLASH CUP: flash cup is not only popular in nightclubs, KTV bars and other places, using flash cup will make you more eye-catching and special. The glitter cups are also very popular among children, and the brilliant colors always attract attention. BATTERY POWERED: The LED light cup is powered by a CR2025 battery. Replacing them when the battery dies seems simple enough. Insert a coin into the battery cover slot, turn it counterclockwise, and it will pop out into the battery compartment. The battery compartment has a rubber or silicone O-ring to keep water out. LIQUID ACTIVATED: Water Induction Color Changing Cup,automatic Water activated. The flashing cup glows automatically when water or drinks are added. It turns off when there is no liquid left. AVAILABLE LIQUID: water, beer, wine, whisky, vodka, martini, drinkware, coffee, tea, etc; LED light would be activated when you pour liquid into the tumbler.