CHEMISTRY-PERFECT - Put the elements from the periodic table to your table. Enjoy a glass of your favorite beverage and place them in these chemistry-inspired coasters featuring the symbols of Radium-226, Plutonium-244, Uranium-238, and Thorium-232. COASTERS THAT LIGHT UP - The coasters light up when you put your drink on them. Included in the pack are eight 3V CR2032 batteries. With constant use, these batteries can last up to 4.5 hours. GREAT AT PARTIES - These coasters are ideal for parties. You will easily remember which drink is yours. IDEAL PRESENT - This is an ideal present to the Chemists in your life, be it a family member, a friend, or a colleague. MADE BY THINKGEEK - The Radioactive Elements Glowing Coaster Set is a ThinkGeek creation. We love chemistry, so we light up when we talk about this product created at ThinkGeek: our Radioactive Elements Glowing Coaster Set. Featuring the atomic number and isotopic mass of the most stable or common isotope for their respective radioactive elements, these pressure-sensitive coasters light up when you put your drink on them. Choose to set your drink down on: Radium-226 (Red), Plutonium-244 (Blue), Uranium-238 (Green), or Thorium-232 (Orange). Set of four comes in a box with the radioactivity warning symbol. Batteries included.