It flashes forever or so you might think. With tunnel lights coasters under your drink. Fill all your guests with sheer fascination. Use tunnel light coasters at your celebration. The transparent mirrors halfway reflect to create an amazing "tunnel effect." Instructions: Light Up Tunnel Coasters have four light-up functions including a rapid-flashing, slow color-changing, still light, and individual flashing colors! Press the clear button located on the back of the coaster to activate and change the light settings. Diameter: 3.75 in. , 9.52 cm. - LED Colors: Blue, Red, Jade - Includes 2 replaceable CR2032 Batteries.