The small blue tile is also called yin-yang tile in the north, and butterfly tile and yin-yang tile in the south, commonly known as Bouwa, which is a kind of curved tile. It is molded by hand, and there is another process after the cooking is the kiln. After the kiln, the chemical reaction takes place before it becomes blue-gray. There are 30×24, 24×20, 20×18 specifications. It is a high-grade ancient construction material for building platforms, palaces, pavilions, pavilions and various garden buildings.

The small blue tiles are composed of hook head, dripping water, tube tiles, slab tiles, Luo Guo, folding waist, lace, tile face and so on.