The color coded weighted balls are small enough and flexible enough to grasp with one hand, yet big enough to hold with two hands. Hand balls increase in weight from 1.1 lb. through 6.6 lbs. (0.5 to 3 kgs.) while maintaining a constant 5" (12.7cm) diameter. Balls are soft and have give, to easily conform to your grasp. Use a bicycle pump to inflate/deflate to make ball harder/easier to grasp.