Gorgeousness meets utility. You'll be guaranteed that your whiskey glass will not be sticking to this coaster. Materials: concrete & recycled glass w/ a cork base Dimensions: 4" w x 5/8" h (per coaster) Our concrete work is all individually hand cast from custom made rubber molds. Colors are integrally mixed into the concrete and results in each piece being unique. Although the sealer is food grade and safe we don't recommend using these for direct food contact. Natural voids occur during casting and some pieces will have very small pin holes. Do not submerge in water. Wipe clean with mild soap and water.