Stress Relief: Scientific research has shown that occupying your hands with a smaller task - like squeezing a rubber ball - allows your brain to relax and stop focusing on what's stressing you out. These balls help promote a sense of calm, reduce stress/anxiety, and can increase focus/attention. Multifunctional: Stress ball on a string, squeeze, pinch, stretch, pull, throw, bounce - they immediately return to their original shape. Squeeze as a finger strengthener stress ball, physical therapy exercise, or hand strength trainer. Size: (5.5cm x 5.5cm), 5 Hardness Levels: Softest (Yellow), Soft (Orange), Medium (Red), Hard (Blue), Hardest (Green). You can choose the appropriate hardness level according to your needs. It is also ideal for "progressive training" that gradually increases the hardness level gradually at the beginning with soft, next medium. Material: The stress ball made of polyurethane. Retains its shape. Extremely durable. Non-toxic, strong, durable, and safe - great stress balls for adults. Makes an excellent gift! Small and Lightweight: The exercise balls are very small. Easy to store in your handbag, briefcase, school bag, even your pocket. You can play it anytime anywhere when you need something to do with your hands. Suitable for age 8+.