When considering finger, thumb, hand and grip strength exercises, we must consider muscle balance. To be clear, stress balls cause stress mechanically. Handmaster Plus is used for finger, thumb, hand and grip strength exercise and comes in three different strengths (soft, medium, firm) depending on individual strength of the user. Dr. Terry Zachary is the developer of Handmaster Plus. Always gain the approval of your health care professional before beginning any finger, thumb, hand, wrist or elbow exercise. Dr. Zachary also illustrates the finger thumb and hand exercise that patients can do for strengthening and rehabilitative exercises with Handmaster Plus. Dr. Zachary also comments on what is wrong with using stress balls to build strength in your hand, wrist, finger and thumb. It doesn't make sense and in fact can build imbalance. Medium strength Handmaster Plus is for finger, thumb, hand, wrist & elbow strength and balance exercises, performance & injury prevention. Firm strength is used for finger, thumb, hand, wrist & elbow strength training exercises specifically.