Stress Reliever: Science research has shown that occupying your hands with a minor task - such as squeezing a rubber ball - allows your brain to relax and stop being focused on whats stressing you. These balls help promote a sense of calm, reduce stress / anxiety and can increase focus / attention. Multifunctional: Stress Ball on a String, smoosh, squeeze, stretch, pull, toss, bounce - they will immediately return to their original shape. Squeeze as a stressball for finger strengthener, physical therapy exerciser, or hand strength trainer. Size: (5.5 cm x 5.5 cm), 5 hardness levels: softest (yellow), soft (orange), medium (red), hard (blue), hardest (green). You can choose the appropriate hardness level as necessary. It is also ideal for "progressive training" which gradually raise the hardness level gradually in the beginning with soft, next medium. Material: The stress ball made of polyurethane. Retain shape. Ultra durable. Non toxic, strong, durable and safe - great stress balls for kids and adults. Makes for a great gift Small and Lightweight: The exercise-balls is very small. Easy to store in your purse, briefcase, school bag, even your pocket. You can play it anytime anywhere when you need something to do with their hands. Stress Ball on a string, smoosh, squeeze, stretch, pull, toss, bounce - they will immediately return to their original shape. As a stressball for finger strengthener, physical therapy exerciser, or hand strength trainer. These balls help promote a sense of calm, reduce stress / anxiety and can increase focus / attention. Place it in your bag and carry it anywhere. It's sharable between family, friends, and colleague. size Each ball is 2.2" in diameter and fits perfectly in the palm of the hands. Material The stress ball made of polyurethane. Non toxic, retain shape,strong,durable and safe. 5-pack stress balls incl. 1 yellow, 1 orange, 1 red, 1 green, 1 blue Portable Double fixed, adjustable hand rope size. You can play it anytime anywhere when you need something to do with their hands.