Go Stones: Slate and Shell Go Stones - Size 36 Biconvex (10.4mm) Genuine Slate and Shell Go stones Shell stones made from high quality Hainan shell (much better quality than the common Mexican shell) Japanese standard size Includes 181 black stones and 180 white stones Stone diameter: 0.87". Stone thickness: 0.41" (2.2 x 1.04 cm). Weight of set: 4.9 lb (2.2 kg).