Our friends at Pretti.Cool say — "Simple, functional and cool. These incense holders are perfect for that end of the day chill routine. 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."