These coasters are accurate atom diagrams for five(5) period 4 transition metals showing the locations of all the electrons in their respective energy levels. This coaster measures 4" in diameter. Included elements: Iron(FE), Zinc(Zn), Titanium(TI), Copper(Cu), and Nickel(Ni). Stay tuned as I'm in the process of designing a holder for this set! Also, if there is a specific element/element set that you would like to see, send me a message or leave a comment and I'll upload those designs.