CanDo Wate Ball
The color coded weighted balls are small enough and flexible enough to grasp with one hand, yet big enough to hold with two hands. Available in 6 weights ranging from 1.1 through 6.6 pounds (0.5 to 3 kg.) while maintaining a constant 5 inch (12.7cm) diameter. Balls are soft and have give to comfortably conform to your grasp. Use a bicycle pump to inflate/deflate to make ball harder/easier to grasp.