Good for training of finger and thumb joints

Many uses, even casually reading.
The red version seems appropriate at moderate discomfort me. The latex-free material feels like firm gelatin and is odorless. Because it is stretchy, it fits all hands of adults, except perhaps for extremely small or extremely large hands.
If the "buttons" facing outward and the incorporated ball in the palm of your hand, you can train the extension of individual fingers and thumb. If the Flex-Gripp playing around (ball upward), you can practice a firm grip and release.
The manual is written in four languages, including English, French, Spanish. - German missing.