STRENGTHENS GRIP AND REDUCES STIFFNESS AND PAIN: Hand therapy exercise balls build strength in the fingers, hands, wrist and forearms, while reducing stiffness and joint pain by stimulating blood circulation in the forearm and hand. Useful for physical and occupational therapy, the balls also provide a sensory outlet for those with ADHD or autism. Perfect for athletes, musicians, office staff and students, as well as those with arthritis, carpal tunnel and rehabilitation needs. PROGRESSIVE RESISTANCE LEVELS: Progressive levels of resistance allows the difficulty of each workout to be gradually increased as your hand strength and grip improves. The color coded set includes an orange extra soft exercise ball, a green soft resistance ball, a blue medium resistance ball and a purple firm exercise ball. Each resistance level can be utilized in interval training, alternating between the four resistance levels in a single workout. PERFECTLY SIZED FOR A COMFORTABLE FIT: Sized to comfortably fit adult hands with an outer diameter of 5 cm. Perfectly sized for grip strength training for both men and women, athletes, musicians, office staff and students, as well as those with arthritis, carpal tunnel, phlebotomy grip and rehabilitation needs. Great for relieving stress and anxiety. DURABLE NONSLIP EXTERIOR: Hand grip therapy balls are constructed with a premium composite material that is odorless and latex free. The lightly textured exterior provides a secure, nonslip surface for gripping. The hand therapy balls retain their shape for extensive usability and are also tear and split-resistant.