All my coasters are 100 x 100 mm and 8 mm tall. The embossed designs are made so that even tall and narrow glasses won’t be in danger of tipping over. The depth allows water to collect in the coaster without making it stick to your cup. All coasters have a cork backing added to them so that they don’t slide on smooth surfaces. They are capable of holding wide coffee cups, and the 4 mm rim means they are also usable as small trays for crafts or knick-knacks. Do not microwave the trays. If your coffee/drink is boiling hot, it may leave a ring on the surface of the coaster.