The coasters are about a 4.75" not perfect square. There are rubber feet on the back to protect table surfaces and a circle is carved into the clay so that the condensation doesn't roll off. This is a coaster that your cup will not stick to because it is not perfectly flat...the circle is also wide enough to place a bottle of wine on.
I have changed the coasters and stock them with the swirl pattern but the old style with etched images are available through special orders.