These coasters are a true work of art, as each one is individually crafted using natural beach sand and pigmented resin to recreate the beauty of a natural beach wave. Not only are they unique and one-of-a-kind, but they are also waterproof and safe to use with hot or cold items. Each coaster is finished with a cork backing to protect both the coaster and the surface it's placed on. Measuring 4" in diameter, these coasters come in a set of four and can also be used as a stunning home décor piece.