If you don't want to buy a coaster set, this is your chance to buy single coasters. Just pick any letter(s) and number(s). Each individual glass tile will come with 4 rubber 'feet' that are glued onto the underside corners so they will not slide. Glass tiles do not absorb the water moisture from your cup. I admit it....glass may not be the best suited material for coasters but these are the most colorful and fun coasters you can buy! Dress up your home or boat with colorful coasters. Spell Anything & Say it With Glass!