Small grey tiles are heavy and prone to breaking, making clay flat tiles a better choice. In northern regions, clay grey tiles are also known as yin-yang tiles, while in southern regions, due to their small size, they are called butterfly tiles. The yin-yang tiles, commonly known as cloth tiles, are curved tiles. Hand-shaped, after firing, a process called wanning kiln is performed, which results in the grey color through a chemical reaction. Available in sizes like 30x24, 24x20, and 20x18. They are high-quality ancient construction materials for building towers, palaces, pavilions, and various gardens. Often used in rural residential buildings, but rarely adopted in important urban buildings.