The Bi-Colour balls are designed to facilitate the assessment of the ball's spinning trajectory. They are ideal for learning and understanding spin, as well as for use in training sessions. They combine two colors in the hemisphere. During the high-speed movement of the ball, they create a visual change that enhances the assessment of the spin. The BI-colour ball has been developed by the Chinese Table Tennis Association (C.T.T.A.) and Double Happiness, using ABS material.