These coasters are 3" square fused glass signal flags. You pick any four letters or numbers for your set of 4 coasters. Two sets of initials are very popular, or try the words "fish", "boat", "sail", "sexy". 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 these nautical signal flags. Spell anything & Say it With Glass! After buying your first initial set of 4 coasters for $45, you may then purchase another 4 at the low price of $10 for each 3" tile. Buy a set for yourself and give a set as a great nautical gift!