Pera Tile UPS-LONDON GRIGO NATURAL 12" x 24" Porcelain Upstone: London Grigio 13.58 Square Feet per Case. Upstone porcelain line celebrates the warm colors of the earth, the oases of the desert and the moon surface. The landscape that surrounds us is reflected in these stones. Upstone is a stone-look large format porcelain product in which the aesthetic qualities and the strong personality are equally balanced. Upstone tiles blend in perfectly with both the traditional style and the more essential lines of contemporary taste.