The Exa-Ball Hand Exerciser is perfect for improving grip, wrist and forearm strength, which is vital for all activities where grip strength is important. Ideal for weightlifting, tennis, golf, rock climbing and all activities where performance is limited by poor grip strength. These hand grippers are also great for rehabilitation, for those recovering from injury and looking to gradually build up strength. They can also be used to relieve stress. These hand exercisers are available in three levels of resistance: light (green), medium (blue) or strong (purple).