Go Stones with Bowls: Size 31 Biconvex Glass Go Stones (8.4mm) Japanese standard size Great value for money Comes with matching plastic bowls Includes 181 black stones and 180 white stones Stone diameter: 0.87". Stone thickness: 0.33" (2.2 x 0.86 cm). Weight of set: 4.9 lb (2.2 kg).