These Mono Serra 12" x 24" porcelain tiles elegantly enhance the look of floors and walls with a glossy grey, marble-like finish. Each box contains 8 tiles, which can cover up to 15.5 sq. ft. It is recommended to install these non-ground tiles with a 1.5 to 3 mm grout joint. These grade-4 tiles include a warranty against any visual defect before installation.