Weight : The smaller the amplitude ,the better control of the ball

Roundness: The smaller of the dispersion between the largest and the smallest diameter is, the more round and the stable the ball is

Hardness: The smaller the hardness number is, the harder & the faster the ball is

Adopt the delicate crafts and the especial materials , STRENGTH brand 40mm table tennis ball is made of the all-round arts and crafts which can decrease the seed and the spin of the ball of the rival & promote the rate of receiving the balls & bring more competition and sports attractiveness