NPT RDM-40 1/2" x 2" Tile Rudiment Sky - With regard to the durability of the bisque and glaze, this material is suitable for: all vertical applications - residential and commercial, all interior walls, fireplace surround and firebox, all exterior wall applications including building facades, swimming pools, fountains and outdoor kitchens. Material can be cleaned with any mild nonabrasive household cleaning product due to the chemical resistant nature of the glaze.