Go and C-Shape Bifacial Convex Go

There are basically two shapes of Go pieces, called Convex One Side and Convex Two Sides.

Convex is common in mainland China, and is the most commonly used shape under the "Chinese rules". The double-sided convex shape is the basic shape of Japanese Go, and the Ying's rules in Taiwan also use the double-sided convex shape, and the tournaments under the Ying's rules absolutely use the specialized Ying's Go (double-sided convex shape) because the number of pieces required for the tournaments is absolutely not less than 180 for each piece. All kinds of tournaments (including professional and amateur tournaments) have a customary rule: use whatever rules you want to play with, so in mainland China, except for Ying-sponsored tournaments, basically single-sided convex pieces are used.