Release Pressure Light Finger Heavy Duty Strength Trainer For AdultsSpecifications:There is no doubt that this ball will stimulate parts of your hands to release pressure and help you strengthen your hand strength, as well as improve your hand posture when playing the piano. Most people can use it because of its 4 different ball sizes, and the light texture makes it comfortable to handle, its soft texture will be comfortable with high elasticity for quick bounce. This will make the plastic comfortable to use. This ball has 4 different sizes for you to choose from. It is suitable for beginners and learners to improve posture and release finger pressure. Item Name: Finger Exercise Ball Material: Plastic Features: High Elasticity, Soft, Comfortable Size Details:Diameter: 5.5cm/2.17" (Approx.) Diameter: 6.5cm/2.56" (Approx.) Diameter: 7.5cm/2.95" (Approx.) Diameter: 9.5cm/3.74" (Approx.) Notes: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Included:1 Set of Finger Ball Exercise (4 Pieces)